1. Lecture 46 Reflection and Refraction of Light Ozgur Unal
NIS – PHYSICAL SCIENCE
Lecture 46
Reflection and Refraction of Light
Ozgur Unal

2. The Interaction of Light and Matter
Objects can absorb light, reflect light or transmit light.
The type of matter in an object determines the amount of light it absorbs, reflects and transmits.
Opaque material  Only absorbs andreflects light
Translucent material  Allows some light to pass through
Transparent material  Transmits almost all the light

3. Reflection of Light Remember the law of reflection
Light reflected from any surface obeys the law of reflection.
Why can you see your reflection in a window but not in a sheet of paper?
The answer has to do with the smoothness of the surfaces.
A smooth even surface reflects the light rays regularly  regular reflection
A rough uneven surface reflects the light rays in different directions  diffuse reflection
Paper has a very rough surface in microscopic scale

4. Reflection of Light
Diffuse reflection is a type of scattering that occurs when light waves travelling in one direction are made to travel in many different directions.
Scattering also occurs when light waves traveling through the air reflect off small particles.

5. Refraction of Light
Waves refract (bend or change direction) when they pass from one medium to another.
The amount of refraction depends on the index of recfaction of the two mediums.
Index of refraction is the ratio of the speed of light in a vacuum to the speed of light in the material.
n = vvacuum / vmaterial
The index of refraction of water is 1.33
The index of refraction of glass is 1.5
What are the speeds of light
in water and glass?

6. Refraction of Light
The higher the difference between the indices of refraction, the larger the light bends when it changes medium.
If there are two different mediums with the same index of refraction, light does not bend.
When the sunlight passes through a prism, it is refracted and also separated into spectrum of colors.
This spectrum of colors is produced because the speed of light in a material also depends on
the wavelength of the light.
Red light is the fastest visible
light  it is refracted the least

7. Refraction of Light
When you’re travelling in a car, have you ever seen what looks like a pool of water on the road ahead?
A mirage is an image of a distant object produced by the refraction of light through the air layers of different density.
Mirages result when the air at ground level is much warmer or cooler than the air above.