TOPIC 5 - EM SPECTRUM Flashcards
What happens when ray of light moves into different material?
It changes speed and direction.
What is the law of reflection?
Angle of incidence=angle of reflection
What is total internal reflection?
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.
What happens when angle of incidence=crticial angle
The reflected light ray passes along the boundary
What is specular reflection?
When light rays are reflected evenly on smooth surfaces.
What is diffuse reflection?
When reflected light is scattered in all directions on rough surfaces.
What is critical angle?
The angle that when angle of incidence reaches this, TIR occurs
What is white light?
Light from the sun (white light) is a mixture of different colours.
How can white light be split up?
Using a prism you can split up white light into colours of the visible spectrum.
Why does a red object look red?
It reflects red light and absorbs all other colours.
How do filters work?
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.
What happens to light rays in a convex lens?
Makes rays CONVERGE (come together) at a focal point
What happens to light rays in a concave lens?
Makes rays DIVERGE (spread out)
What is the focal point in a concave lens
The point which rays seem to be coming from after passing through lens Wha
What is focal length?
Distance between focal point and centre of lens
What happens if body radiates less power than power absorbed?
The temperature decreases
How does the Earth naturally warm its atmosphere?
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.
How can the Earth stay at the same temperature?
It must radiate energy into space at the same rate that it absorbs it.
What is the Earth’s energy balance?
The amount of energy leaving the atmosphere is same as the amount entering.
What is the greenhouse effect?
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.
What is electromagnetic radiation?
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.
