PHYSICS

RADIATION

Blogger's note: The information I posted aren't mine. They were all taken during our discussion in our Advanced Physics II class with Mr. Mohamad Ali Ramber and some additional informations from the internet (sources cited at the end of each post). The pictures and animations aren't also mine. Credits to the rightful owners who placed it in google This was the summary of our whole discussions during our second quarter in our class.

Wilhelm Conrad Roentgen -discovered x-rays on 1895. He discovered that x-rays can be generated by directing a cathode ray tube against the wall of a glass tube.

Antoine Henri Becquerel -discovered "radioactivity". He also had serendipitous discovery of the phenomenon "invisible phosphorescence.

Marie Curie -coined the term "radioactivity" and validated Becquerel's "the higher the proportion of uranium in the sample, the more intense the radiation is emitted. She predicted that there's a presence of one or more radioactive elements in the core. She was joined by her husband Pierre Curie. They both isolated two radioactive elements, polonium and radium (2M times more radioactive than uranium).

ALPHA, BETA, GAMMA

Ernest Rutherford found two distinct types of radiation: alpha and beta.

Alpha rays - can be deflected using strong electric and magnetic fields, they were determined to have a charge of +2. Alpha particles are helium nuclei.

Beta rays - determined to have a charge of -1. Beta particles are electrons.

Gamma rays - electromagnetic, like light. It has no charge and no mass. Basically, their photons are the same as light and x-ray photons. However, gamma ray is given to the photons emitted from the nucleus during the gamma decay process.

Ernest Rutherford and Frederic Soddy first proposed that radioactivity produces new elements.

Isotope -the same element but different mass numbers: same number of protons, diffferent number of neutrons.

MECHANISMS OF RADIOACTIVE DECAY

Decay chains/series -decay process in which other radioactive nuclei undergo a series of nuclear transformations before attaining a stable isotope. (e.g. uranium series, thorium series, actinium series, neptunium series)

Half-life -time interval during which half of the atoms originally present disintegrate. It is a fundamental and constant property of a radionuclide. IT cannot be altered by temperature or pressure changes nor by chemical reactions. It is a measure of the stability of the nuclei. A short half-life means an unstable nucleus.

Cosmic Radiation -interaction of cosmic rays with the upper layers of earth's atmosphere.

Terrestrial Radiation -due to the presence of highly radioactive substance rising to the Earth's surface.

Geiger Counter -most common instrument to detect radiation.

Radiation Dose -amount of energy absorbed per kilogram of an irradiated object at the actual target site.

ACUTE vs LONG-TERM EFFECTS

In general, the amount and duration of radiation exposure affects the severity or type of health effect. There are two broad categories of health effects: stochastic (long-term) and non-stochastic (acute/ short-term).

Non-Stochastic/Acute Health Effects

Non-stochastic effects appear in cases of exposure to high levels of radiation, and become more severe as the exposure increases. Short-term, high-level exposure is referred to as ‘acute’ exposure.

Many non-cancerous health effects of radiation are non-stochastic. Unlike cancer, health effects from ‘acute’ exposure to radiation usually appear quickly. Acute health effects include burns and radiation sickness. Radiation sickness is also called ‘radiation poisoning.’ It can cause premature aging or even death. If the dose is fatal, death usually occurs within two months. The symptoms of radiation sickness include: nausea, weakness, hair loss, skin burns or diminished organ function.

Medical patients receiving radiation treatments often experience acute effects, because they are receiving relatively high “bursts” of radiation during treatment.

Stochastic/Long-Term Health Effects

Stochastic effects are associated with long-term, low-level (chronic) exposure to radiation. (“Stochastic” refers to the likelihood that something will happen.) Increased levels of exposure make these health effects more likely to occur, but do not influence the type or severity of the effect.

Cancer is considered by most people the primary health effect from radiation exposure. Simply put, cancer is the uncontrolled growth of cells. Ordinarily, natural processes control the rate at which cells grow and replace themselves. They also control the body’s processes for repairing or replacing damaged tissue. Damage occurring at the cellular or molecular level, can disrupt the control processes, permitting the uncontrolled growth of cells–cancer. This is why ionizing radiation’s ability to break chemical bonds in atoms and molecules makes it such a potent carcinogen.

Other stochastic effects also occur. Radiation can cause changes in DNA, the “blueprints” that ensure cell repair and replacement produces a perfect copy of the original cell. Changes in DNA are called mutations. Sometimes the body fails to repair these mutations or even creates mutations during repair. The mutations can be teratogenic or genetic. Teratogenic mutations are caused by exposure of the fetus in the uterus and affect only the individual who was exposed. Genetic mutations are passed on to offspring.

RADIATION APPLICATIONS

• Food and Agriculture
• Ionizing radiation -mutation, production of new genetic lines of rice, garlic, wheat, etc.
• Food irradiation -form of preservation
• Sterile Insect Technique
• Diagnosis and Therapy
• Radioisotopic Tracing -diagnosis strategy using small amounts of short-lived radioactive isotopes injected into the patient's body.
• Radioactive Dating
• Uranium Dating -determine age of Earth, solar system, moon
• Carbon dating - uses Carbon-16. Determines the age of plants and animal remains.

Albert Einstein predicted the coming of nuclear age through his Theory of Relativity.

NUCLEAR REACTORS

Parts of Nuclear Power Plant

A Nuclear Reactor mainly consists of
a) Fuel      
b) Moderators           
c) Control rods            
d) Shielding       
e) Coolant     
f) Turbines    
g) Generator     
h) Cooler Pipes      
i) Water Supply

Fuel:The fissionable material used in the reactor is called as fuel. The  commonly used fuels are Uranium, Plutonium or Thorium. It can be U-235, U-238, Pu-236 or Th-232. Uranium is mostly preferred as it has high melting point.

Moderators:Only neutrons of a fairly low speed should be used to have controlled chain reaction. To slow down the speed fast moving neutrons produced during the fission process, moderators are used. Moderator reduces the speed of the neutron by absorbing its energy but not absorb neutron. Graphite, Heavy water and Beryllium are common moderators.

Control Rods:These rods absorb neutrons and stop the chain reaction to proceed further. These are made up of steel containing a high percentage of material like cadmium or boron which can absorb neutrons. When control rods are completely inserted into the moderator block then all the neutrons is absorbed and reaction comes to halt.

Shielding:Shielding prevents radiations to reach outside the reactor. Lead blocks and concrete enclosure that is strong enough of several meters thickness are used for shielding.

Coolant:The coolant is substance in a pipe to the steam generator where water is boiled. This is where heat-exchange process occurs. Heat is absorbed by the coolant that is produced in the reactor. Typical coolants are water, carbon dioxide gas or liquid sodium.

Turbines:Steam produced in the boiler is now passes to a turbine. The force of the steam jet causes the turbine to rotate. Heat energy (steam) is converted to mechanical energy (moving turbine).

Generator:The generator consists of coils that change the mechanical energy into electric energy. The turbine moves and the change in magnetic flux cause electricity. This is transmitted to substations for distribution of
electric power.  

Sources: 

INTERACTIVE PHYSICS NOTEBOOK 2014-2015

http://www.tutorvista.com/physics/ten-parts-of-a-nuclear-power-plant

http://www.celebritydiagnosis.com/2011/03/lester-holt-steps-in-it-shoes-test-positive-for-radiation-exposure/

PHYSICS

THE HUMAN EYE

• The Human Eye With this presentation, we will tackle about the following: a. Parts of the Human Eye b. Functions of the Parts c. Defects of the Human Eye
• Fundamental Parts of the Human Eye
• Functions of the Parts of the Human Eye The human eye is the sense organ which helps us to see the colorful world around us. The human eye is like a camera. Its lens system forms an image on a light sensitive screen called retina. The eye ball is almost spherical in shape with a diameter of about 2.3cm. Light enters the eye through a transparent membrane called cornea. Behind the cornea is a muscular diaphragm called iris which has an opening called pupil. The pupil controls the amount of light entering the eye. The eye lens helps to focus the image of objects on the retina. The ciliary muscles helps to change the curvature of the lens and to change its focal length.
• The macula allows us to appreciate detail and perform tasks that require central vision such reading. The vitreous humor comprises a large portion of the eyeball. It is a clear gel that occupies the space behind the lens and before the retina at the back of the eye. Because the eye must process visual data, this liquid must be clear enough that light can easily pass through. The optic nerve transmits electrical impulses from the retina to the brain. It connects to the back of the eye near the macula.
• Human Eye Defects Myopia (Near Sightedness) is a defect of vision in which a person can see nearby objects clearly but cannot see distant objects clearly because the image is formed in front of the retina. This may be due to : i) Increase in curvature of the eye lens ii) Increase in the length of the eye ball It can be corrected by using suitable concave lens. Myopic eye Correction using concave lens
• Hypermetropia (Far Sightedness) is a defect of vision in which a person can see distant objects clearly but cannot see nearby objects clearly because the image is formed behind the retina. This may be due to:- i) Decrease in curvature of eye lens ii) Decrease in the length of the eye ball It can be corrected by using a suitable convex lens. Hypermetropic eye Correction using convex lens
• Presbyopia is a defect of vision in old people in which they are not able to see nearby objects clearly due to the increase in the distance of near point. This is due to the weakening of the ciliary muscles and decrease in the flexibility of the eye lens. It can be corrected by using suitable convex lens. Sometimes they are not able to see both nearby and distant objects clearly. It can be corrected by using bifocal lenses consisting of both concave and convex lenses. The upper part is concave for correction of distant vision and the lower part is convex for correction of near vision.
• Astigmatism is a defect in the eye when the light rays do not all come to a single focal point on the retina, instead some focus on the retina and some focus in front of or behind it. This is usually caused by a non-uniform curvature of the cornea. A typical symptom of astigmatism is if you are looking at a pattern of lines placed at various angles and the lines running in one direction appear sharp whilst those in other directions appear blurred. Astigmatism can usually be corrected by using a special spherical cylindrical lens; this is placed in the out-of-focus axis.
• A cataract is a clouding of the lens, which prevents a clear, sharp image being produced. A cataract forms because the lens is sealed in a capsule and as old cells die they get trapped in the capsule, with time this causes a clouding over of the lens. This clouding results in blurred images.
• Age-related Macular Degeneration (ARMD) is a degenerative condition of the macula (the central retina). It is caused by the hardening of the arteries that nourish the retina. This deprives the retinal tissue of the nutrients and oxygen that it needs to function and causes a deterioration in central vision.
• Glaucoma is a disease caused by increased IOP usually resulting from a malfunction in the eye’s drainage system. The eye produces a clear fluid (aqueous humor) that fills the space between the cornea and the iris. This fluid filters out through a complex drainage system. It is the balance between the production and drainage of this fluid that determines the eyes intraocular pressure (IOP). Increased IOP can cause irreversible damage to the optic nerve and retinal fibers and if left untreated can result in a permanent loss of vision.

PHYSICS

Blogger's note: The information I will be posting today aren't mine. They were all taken during our discussion in our Advanced Physics II class with Mr. Mohamad Ali Ramber. The pictures and animations aren't also mine. Credits to the rightful owners who placed it in google

LIGHT

Light behaves as a particle and a wave. Soundwaves travel through air (medium). Light has no medium (wave property). Photons make up light (particle property)

Energy in each photon is based on frequency.

E = hf, where h is Plank's constant which is approximately equal to 6.626 x 10^-34 J.S

Blue light bends most while red light bends the least.

CORPUSCULAR THEORY OF LIGHT (1704)

• Isaac Newton
• Contains a stream of small particles
• Travels in straight lines at great speeds
• reflected from mirrors in a predictable way

WAVE THEORY OF LIGHT

• Thomas Young
• Light is a wave
• undergoes diffraction and interference (Young's double-slit experiment)

LIGHT AS PARTICLE

• position "x", momentum p=mv, mass "m"

LIGHT AS WAVE

• wavelength, amplitude, frequency

WAVES vs PARTICLES

• a particle is localized in space and has discrete physical properties such as mass.
• Wave is inherently spread out, could have amplitudes in a continuous range
• waves superpose and pass through each other, while particles collide and bounce off each other.

Diffraction

 -spreading out of the plane waves as they pass through a hole.

Interference

1. Constructive Interference - occurs where wave crests meet
2. Destructive Interference - occurs where wave crest and trough meet.

BLACKBODY RADIATION

• Blackbody is an object which totally absorbs all radiation that falls on it
• Any hot body radiates light over the whole spectrum of frequencies

PHYSICS

This week, we had a series of test for evaluation of what we learned throughout the past  months. We were given series of problems that we have to solve dealing with index refractions, mirrors, mirror equations, lens, lens equations even the compound lenses.

We also had a chapter test which pretty much summarizes everything we discussed.

We also had this new agreement that in every chapter test, one should get at least 75 percent of the number of items correct or else they will have remedial classes.

However, remedial classes aren't that bad, are they? :)

xoxo

-Ronna

PHYSICS

IMAGE FORMATION FOR CONVERGING LENSES

IMAGES FORMED IN DIVERGING LENSES

PHYSICS

Blogger's note: The information I will be posting today aren't mine. They were all taken during our discussion in our Advanced Physics II class with Mr. Mohamad Ali Ramber. The pictures and animations aren't also mine. Credits to the rightful owners who placed it in google.

LENS

Lens are two reflective surfaces joined together. There are two types of lenses: diverging lens and converging lens.

3 Types of Converging Lenses and Diverging Lenses

Converging lenses collects light and lets them converge in one point.

Diverging lenses scatters light, thus the word.

Note: If the distance of the object is infinite, the image formed is a point.

Equation:

Sign conventions:

Note: Converging Lens are positive lens whereas diverging lens are negative lens.

PHYSICS

Blogger's note: The information I will be posting today aren't mine. They were all taken during our discussion in our Advanced Physics II class with Mr. Mohamad Ali Ramber. The pictures and animations aren't also mine. Credits to the rightful owners who placed it in google.

INDEX OF REFRACTION

Refraction is the bending of light.

• Light decreases speed as it enters water
• Light bends when it enters a region of different density.
• The two situations above are under the "optical density"

Formula of Index of Refraction: n = c/v where n= index of refraction, c=speed of light in vacuum (3.0x10⁸ m/s), v = speed of light in the medium

Indices of Refraction

1. Vacuum - 1.0000
2. Air - 1.0003
3. Water - 1.33
4. ethyl Alcohol - 1.36
5. Glass (fused quartz)  - 1.46
6. Crown Glass - 1.52
7. Light flint - 1.58
8. Flexiglass - 1.51
9. Sodium chloride - 1.53
10. Diamond - 2.42

Note that the index of refraction is NEVER less than the value of 1.

REFRACTION: SNELL'S LAW

• Light speed decreases if it travels from a region with lower than 1.0 index of refraction to a higher index of refraction.

Willebrord Snell in 1621

If n₂ < n₁, then θ₂ > θ₁ the ray then BENDS AWAY from the normal line.

Law of refraction: The incident and refracted rays lie in the same plane.

JUST FOR EMERGENCY AND FOR REMINDER IN CASE ANOTHER TEST LIKE THIS WILL BE GIVEN:

PHYSICS

Blogger's note: The information I will be posting today aren't mine. They were all taken during our discussion in our Advanced Physics II class with Mr. Mohamad Ali Ramber. The pictures and animations aren't also mine. Credits to the rightful owners who placed it in google.

II. CONVEX MIRRORS

Note: Image is always smaller in a convex mirror.

Image formation:

Most of the time, convex mirrors form a reduced, upright and virtual image.

PHYSICS

Blogger's note: The information I will be posting today aren't mine. They were all taken during our discussion in our Advanced Physics II class with Mr. Mohamad Ali Ramber. The pictures and animations aren't also mine. Credits to the rightful owners who placed it in google.

SPHERICAL MIRRORS (CURVED MIRRORS)

I. CONCAVE MIRRORS

where: C - center of curvature, O - object, F- principal focus, f - focal length, v- vertex

Note: If the incident ray is parallel, reflected ray passes through F. If it passes F, reflected ray is parallel. And if it passes C, the reflected ray is still at C.

Defining an image: Is it real or virtual? Where is it located? Is it reduced or enlarged? Is it inverted or upright?

You can identify whether the image is reduced or larged by simply looking at the ray diagram. In the second picture, you can see that the image formed, labeled 'I', is larger than the object 'O' thus the "enlarged" in the definition.

PHYSICS

Blogger's note: The information I will be posting today aren't mine. They were all taken during our discussion in our Advanced Physics II class with Mr. Mohamad Ali Ramber. The pictures and animations aren't also mine. Credits to the rightful owners who placed it in google.

"Mirror, mirror on the wall, who is the fairest of them all?"

Where did the queen in the story Snow White say this? To the mirror.

When you want to check if you still look presentable, where do you look? Of course on the mirror or anything that will reflect your image.

Everyday day in our everyday lives, we always use MIRRORS. Although mirrors are not only used solely for seeing your own reflection, facing the mirror to see our own self is one of the most common practical uses of mirror in which almost everyone in this world does.

REFLECTION AND IMAGE FORMATION

There are different kinds of mirror. Some of these examples are the flat or plane mirror, concave mirror and convex mirror.

The Law of Reflection

• The angle of incidence is equal to the angle of reflection: θ_i  = θ_r
  
• the incident and reflected lines lie in the same plane with the normal line to the surface

Animation: http://64.19.142.13/www.physicsclassroom.com/mmedia/optics/lr.gif

Types of Reflection

1. Regular reflection - reflection on smooth surface

2. Dispersed/Scattered Reflection - reflection on rough surfaces

Characteristics of images formed in mirror:

• laterally reversed
• virtual image (as if the image is found behind the mirror; cannot be projected on screen)
• The same size and distance with the real image

Image Formation