(P1) Topic 5- Light And The Electromagnetic Spectrum

Question 1

Angle of incidence is (?) to angle of reflection

Answer 1

Equal to

Question 2

Why can only very smooth surfaces reflect

Answer 2

If the surface is bumpy then the light is not reflected evenly

Question 3

What is specular reflection

Answer 3

When all light rays are parallel and an image is formed

Question 4

What is diffuse reflection

Answer 4

When light reflects off a surface that isn’t flat and no image is formed

Question 5

What is a virtual image

Answer 5

an upright image that is achieved where the rays seem to diverge (isn’t real)

Question 6

What does a convex lens do

Answer 6

Brings light rays closer together (they converge)

Question 7

What does a convex lens look like

Answer 7

()

Question 8

What is a convex lens used for

Answer 8

Long-sightedness

Question 9

Where is the focal point of a convex lens

Answer 9

After the lens

Question 10

What does a concave lens do

Answer 10

Spreads out light rays (diverges rays)

Question 11

What are concave lenses used for

Answer 11

Short-sightedness

Question 12

Where is the focal point of a concave lens

Answer 12

Before the lens

Question 13

Define focal point

Answer 13

the point at which rays or waves meet after reflection or refraction, or the point from which diverging rays or waves appear to proceed

Question 14

Define focal length

Answer 14

The distance between the centre of the lens and the focal point

Question 15

What does it mean is light rays cross with imaginary lines on a diagram

Answer 15

The image is virtual, not real

Question 16

What does a concave lens look like

Answer 16

)(

Question 17

What are the rules for converging lens (convex)

Answer 17

-if ray goes to centre of lens, it keeps going straight
-ray parallel= through to focal point on right

Question 18

What are the rules for diverging lenses (concave)

Answer 18

-if ray goes to the centre it keeps going straight
-ray parallel= through to focal to focal point on left

Question 19

Calculation for optical power

Answer 19

Optical power= 1 / focal length

Question 20

What is optical power

Answer 20

How strong a lens is

Question 21

What are the EM spectrum waves made by

Answer 21

Vibrating electric and magnetic fields

Question 22

What is the speed of all EM waves

Answer 22

3x10^8

Question 23

EM waves are (?) waves

Answer 23

Transversal

Question 24

EM spectrum in order, from long wavelength+low energy+low frequency to short wave+high energy+high frequency

Answer 24

Radio waves
Microwaves
Infrared
Visible light
Ultra-violet
X-rays
Gamma rays

Question 25

Radio waves

Answer 25

-produced by oscillations in electrical currents -information coded into the wave -long wavelength, low frequency

Question 26

Microwaves

Answer 26

-beamed up to a satellite which reflect back down into a device -phone -> electrically charged satellite -> transmitter

Question 27

Infrared

Answer 27

-photothermal heating -the internal energy of the bonds increases when they absorb infrared, which causes heating -incident later light -> reflected and IR emissions, emitted IR radiation -> infrared detector

Question 28

Ultraviolet

Answer 28

-fluorescent. Substances absorb ultraviolet light and re-emit the energy as visible light -shorter wavelength and higher energy than visible light

Question 29

X-Rays

Answer 29

-X-rays are transmitted through body tissues with very little absorption, whereas dense structures absorb them. This shows up as an image on the screen

Question 30

What happens in an object when it is heated

Answer 30

The particles in the object move faster as they gain energy

Question 31

What is 0 kelvin

Answer 31

-273.15 degrees Celsius -particles have no energy and don’t move at all

Question 32

What does energy per second equal

Answer 32

Power

Question 33

What would happen to the infrared that the earth absorbs from the sun if there was no atmosphere

Answer 33

The night side would emit al of the infrared

Question 34

Infrared radiation core practical

Answer 34

Speed of cooling- water in 4 test tubes, one control, on in tin foil, one in white paper, one in black paper. See which one cools to room temp the slowest = best insulator

Question 35

Danger level of radio waves

Answer 35

Very low danger

Question 36

Danger level of microwaves

Answer 36

Low intensity (e.g mobile signals)- unlikely to cause danger High intensity (e.g microwaves oven)- cooks your insides, very high danger

Question 37

Danger level of infrared

Answer 37

Intense source- causes burns

Question 38

Danger of visible light waves

Answer 38

Intense sources (e.g looking at the sun)- destroys your retina and can cause blindness

Question 39

Danger of ultraviolet waves

Answer 39

Can cause sunburn and skin cancer

Question 40

Danger of x-rays

Answer 40

Ionising radiation- can cause cancer as cells can be altered Large dose leads to DNA breakdown, radiation sickness

Question 41

Danger of gamma rays

Answer 41

Same as x-rays Ionising radiation- can cause cancer as cells can be altered Large dose leads to DNA breakdown, radiation sickness