Sunday, January 31, 2010
REFRACTION
-When light rays travels from one medium to another medium of different density. The light ray changes it direction and bends. The bending of light is called refraction.
5:30 PM
Thursday, January 28, 2010
Tracing reflected light rays:
-The perpendicular line to the surface NO is the normal
-The perpendicular line to the surface NO is the normal-A ray of light AO strikes the mirror at point O, creating an angle i with the normal. AO is called the incident ray, and angle i is called angle of incidence.
-The light ray that bounces off the mirror and leaves along the path OB. OB is called the reflected ray. This ray makes an angle r with the normal. This angle is called the angle of reflection.
Types Of Mirror:
-Plane Mirrors
-Concave Mirrors
-Convex Mirrors
Plane Mirrors:
-Commonly used to check one's appearance
-Used as a form of decoration to make a room more spacious
-Used in cars as rear-view or side-view mirrors.
Concave Mirrors:
-Mirrors with curved surfaces that bend inwards.
-When object is nearer to mirror, image formed are virtual and bigger.
Convex Mirrors:
-Mirrors that bend outwards
-Covers a wider field of vision, and the images formed are distorted and smaller.
3:25 AM
(CONTINUED)
Reflection in Mirror:
Plane Mirrors
-Flat mirror that is usually found at home.
-Good Reflector Of light
Characteristics if Plane Mirror images:
-Distance of the image from the mirror is equal to the distance of the object from the mirrior.
-Image and object are of the same size.
-Image is upright.
-Image is laterally inverted.
Image is virtual.
Reflection in Mirror:
Plane Mirrors
-Flat mirror that is usually found at home.
-Good Reflector Of light
Characteristics if Plane Mirror images:
-Distance of the image from the mirror is equal to the distance of the object from the mirrior.
-Image and object are of the same size.
-Image is upright.
-Image is laterally inverted.
Image is virtual.
3:08 AM
Friday, January 8, 2010
Here are 2 questions asked during physics lesson today:
Question one:
Why does the test tube disappear in the boiling tube when glycerin is poured in?
Answer:
This is because glycerin has the same refractive index as glass, so any light that passess through is bent equally. Since both glycerin and glass is transparent, its impossible for the eye to differciate the boundary by a change in the angle of refraction, therefore, the glass seems to disappear.
Question one:
Why does the test tube disappear in the boiling tube when glycerin is poured in?
Answer:
This is because glycerin has the same refractive index as glass, so any light that passess through is bent equally. Since both glycerin and glass is transparent, its impossible for the eye to differciate the boundary by a change in the angle of refraction, therefore, the glass seems to disappear.
Question Two:
Are sport drinks like 100 plus, gatorade, powerade acidic ?
Answer:
I searched the internet and couldn't find a direct answer to this question. If you do look at the ingriedients on the label, many sport drinks such as 100 plus, gatorade and other sport drinks, they contain citric acid and salts which are combinations of electrolytes such as sodium, potassium and chloride. An electrolyte is a substance which dissociates free ions when dissolved, to produce an electrically conductive medium. Because they generally consist of ions in solution, electrolytes are also known as ionic solutes. Electrolytes generally exist as acids, bases or salts. Therefore, sport drinks can be acidic.
source:
6:40 PM
Chapter 17 - Light
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REFLECTION
Light is a form of energy. Light travels in straight lines. Light in a vacuum travels 300,000,000 m/s.
Rays and Beams
Light rays is the path of light from a source. A bundle of light rays is known as a beam of light. Beams of light can be parallel, divergent or convergent.
REFLECTIONRegular Reflection
- when light rays hit smooth surface
- clear and undistorted image can be seen
- parallel beam of light remains parallel after regular reflection.
Irregular/Diffuse Reflection
- when light rays hit rough surface
-no reflected image seen
- parallel beam of light hits rough surface, gets scattered or reflected in an irregular manner..JPG)
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Periscopes
- made of two plane mirrors to see over obstacles .JPG)
3:45 AM
Tuesday, January 5, 2010
HELLO!!
Back to post after a long long long time.
Some questions asked at PHYSICS lesson today:
QUESTION ONE: Why does ice stick to your skin?
As everyone knows, ice is made from water, H2O. It is composed by two hydrogen atoms to a single oxygen atom. These atoms are arranged in a "V-shape" with the hydrogens at the tips of the "V" and the oxygen at the point. Oxygen has two extra pairs of electrons - two "lone pairs" - that dangle from it so that the water molecule is actually a "tetrahedron". (A tetrahedron is a four side solid figure, with four points.) When the water molecules interact when one of the lone pairs on an oxygen reaches out for the hydrogen atom on an adjacent water molecule. This is called "hydrogen bonding" and it is why water is a liquid at room temperature and not a gas.
All of the water molecules are connected with their neighbours through hydrogen bonding interactions.Water molecules interact when one of the lone pairs on an oxygen reaches out for the hydrogen atom on an adjacent water molecule. This is called "hydrogen bonding" and it is why water is a liquid at room temperature and not a gas. All of the water molecules are connected with their neighbours through hydrogen bonding interactions.
As the surface of the ice, there are going some water molecules that line the surface with their oxygen atoms facing outwards.These oxygens will not be able to "hydrogen bond" with any other water molecules because they are at the surface and there are no more water molecules to bond with.And some water molecules will be at the surface with their hydrogen atoms pointing out. They will also be looking for a partner to bond with but will be left unsatisfied.
The result is that at a molecular level there are an awful lot of molecules that are left searching for a partner to join with in a hydrogen bonding arrangement. When ice comes in contact with another surface that is capable of forming hydrogen bonds, then it will stick to that surface. Your skin has a fairly high moisture content and is therefore very suitable for forming these interactions therefore, sometimes ice sticks to your skin.
QUESTION ONE: Why does ice stick to your skin?
As everyone knows, ice is made from water, H2O. It is composed by two hydrogen atoms to a single oxygen atom. These atoms are arranged in a "V-shape" with the hydrogens at the tips of the "V" and the oxygen at the point. Oxygen has two extra pairs of electrons - two "lone pairs" - that dangle from it so that the water molecule is actually a "tetrahedron". (A tetrahedron is a four side solid figure, with four points.) When the water molecules interact when one of the lone pairs on an oxygen reaches out for the hydrogen atom on an adjacent water molecule. This is called "hydrogen bonding" and it is why water is a liquid at room temperature and not a gas.
All of the water molecules are connected with their neighbours through hydrogen bonding interactions.Water molecules interact when one of the lone pairs on an oxygen reaches out for the hydrogen atom on an adjacent water molecule. This is called "hydrogen bonding" and it is why water is a liquid at room temperature and not a gas. All of the water molecules are connected with their neighbours through hydrogen bonding interactions.
As the surface of the ice, there are going some water molecules that line the surface with their oxygen atoms facing outwards.These oxygens will not be able to "hydrogen bond" with any other water molecules because they are at the surface and there are no more water molecules to bond with.And some water molecules will be at the surface with their hydrogen atoms pointing out. They will also be looking for a partner to bond with but will be left unsatisfied.
The result is that at a molecular level there are an awful lot of molecules that are left searching for a partner to join with in a hydrogen bonding arrangement. When ice comes in contact with another surface that is capable of forming hydrogen bonds, then it will stick to that surface. Your skin has a fairly high moisture content and is therefore very suitable for forming these interactions therefore, sometimes ice sticks to your skin.
Ice (:
QUESTION TWO: Why won't the lift activate when you wear gloves to press the lift button or when you touch a touch-screen pannel?
For this question, i can't find any answers to it. But i think the lift or touch screen things cannot activate when we wear gloves to press the buttons as i think heat is involved in this. As you all know, heat travels from hotter region to a cooler region. Therefore, the heat from our finger travels from the finger to the cool lift button or the cool touch-screen surface thus, the heat will activate the sensors in the lift and touch-screen things.
But when you wear the gloves, the heat from your finger could not pass through the thick material the glove is made from to the sensor in the lift button and the touch-screen objects.
Remote control
9:17 PM
