TOPIC 5 - EM SPECTRUM

Question 1

What happens when ray of light moves into different material?

Answer 1

It changes speed and direction.

Question 2

What is the law of reflection?

Answer 2

Angle of incidence=angle of reflection

Question 3

What is total internal reflection?

Answer 3

When the angle of incidence is larger than the critical angle so light ray is completely reflected inside glass. The ray must be moving from high to low density.

Question 4

What happens when angle of incidence=crticial angle

Answer 4

The reflected light ray passes along the boundary

Question 5

What is specular reflection?

Answer 5

When light rays are reflected evenly on smooth surfaces.

Question 6

What is diffuse reflection?

Answer 6

When reflected light is scattered in all directions on rough surfaces.

Question 7

What is critical angle?

Answer 7

The angle that when angle of incidence reaches this, TIR occurs

Question 8

What is white light?

Answer 8

Light from the sun (white light) is a mixture of different colours.

Question 9

How can white light be split up?

Answer 9

Using a prism you can split up white light into colours of the visible spectrum.

Question 10

Why does a red object look red?

Answer 10

It reflects red light and absorbs all other colours.

Question 11

How do filters work?

Answer 11

Coloured light is produced using filters, transparent material that absorbs some colours of white light. E.g. in a blue filter, blue filter transmits and absorbs all other colour.

Question 12

What happens to light rays in a convex lens?

Answer 12

Makes rays CONVERGE (come together) at a focal point

Question 13

What happens to light rays in a concave lens?

Answer 13

Makes rays DIVERGE (spread out)

Question 14

What is the focal point in a concave lens

Answer 14

The point which rays seem to be coming from after passing through lens Wha

Question 15

What is focal length?

Answer 15

Distance between focal point and centre of lens

Question 16

What happens if body radiates less power than power absorbed?

Answer 16

The temperature decreases

Question 17

How does the Earth naturally warm its atmosphere?

Answer 17

The surface absorbs half the radiation that reaches it from the Sun. It re-radiates this energy as infrared radiation, which can warm up the atmosphere.

Question 18

How can the Earth stay at the same temperature?

Answer 18

It must radiate energy into space at the same rate that it absorbs it.

Question 19

What is the Earth’s energy balance?

Answer 19

The amount of energy leaving the atmosphere is same as the amount entering.

Question 20

What is the greenhouse effect?

Answer 20

Some gases in the atmosphere (greenhouse gases) like CO2, absorb some energy keeping the Earrth at high temperatures. These gases are breaking Earth’s energy balance.

Question 21

What is electromagnetic radiation?

Answer 21

It is radiation produced by changes in the electrons or nuclei in atoms. Heating cuases changes in electron arrangement so so produces infrared radiaiton.
Changes in nuclei produce gamma radiation.