P1.8/9 - Electromagnetic waves

Question 1

What do waves do?

Answer 1

All types of waves transfer energy from one place to another.

Question 2

Waves are made up of a series of __________ or vibrations travelling through space.

Answer 2

oscillations

Question 3

What is a transverse wave?

Answer 3

A transverse wave is a wave in which the oscillations are always at right angles to the direction of the wave motion.

Question 4

What is the amplitude of a wave?

Answer 4

The maximum height of the wave measured from the middle. Measured in metres.

Question 5

What is the wavelength of a wave?

Answer 5

The shortest distance between one point and the same point on the next wave. Measured in metres.

Question 6

What is the frequency of a wave?

Answer 6

The number of waves passing a point per second (or number of oscillations a second). A frequency of 6 Hz means that 6 waves passes a point every second. Measured in hertz (Hz).
kHz = Kilohertz
MHz = Megahertz

Question 7

The speed of a wave depends on its frequency and wave length. What calculation can you use to find the speed of a wave?

Answer 7

wave speed (m/s) = frequency (Hz) x wavelength (m)
λ= wavelength (Greek letter lam-da)
v= wave speed
f= frequency

Question 8

Give three examples of electromagnetic waves

Answer 8

• Light
• Microwaves
• X-rays

Question 9

If electromagnetic(EM) waves don’t need a medium to travel through, they can travel through a ______, e.g space.

Answer 9

vacuum

Question 10

How does light and infrared rays reach the Earth from the Sun?

Answer 10

They reach the Earth as they do not need a medium to travel through, which means they can travel through a vacuum (space) towards Earth.

Question 11

What is the electromagnetic spectrum?

Answer 11

The electromagnetic spectrum is a family that the different types of electromagnetic waves are put into.

Question 12

List the electromagnetic waves in the EM spectrum from longest to shortest.

Answer 12

(longest) Radio waves, microwaves, infrared rays, visible light, ultraviolet, X-rays and gamma rays (shortest)

Question 13

How do electromagnetic waves travel? (speed, pattern)

Answer 13

All electromagnetic waves travel at the speed of light (300,000,000 m/s) and they all travel in straight lines despite having different frequencies, wavelengths and amplitudes.

Question 14

How can you see yourself in a mirror?

Answer 14

When you look in a mirror light waves reflect off of the mirror showing your reflection on it. However, all waves can be reflected not just light waves.

Question 15

The law of reflection states that the angle of incidence is always (i)_____ to the angle of reflection. Even if the surface is really rough, the (ii)___ angles are still the same.

Answer 15

(i) equal

(ii) two

Question 16

What is refraction?

Answer 16

Refraction is when waves go from one medium to another and change speed, which causes them to change direction. This is why a pencil can look bent when placed in water. If they wave speeds up it bends away from the normal, if the wave slows down it bends towards the normal.

Question 17

What is the normal?

Answer 17

The intersecting a given line or surface at right angles.

Question 18

What is diffraction?

Answer 18

Diffraction is whenever a wave passes through a gap or moves around an obstacle. Whenever a wave goes through a gap (a door for example) or an obstacle it spread out. This is why you can still hear someone talking if they are outside and you are inside.

Question 19

What problems can be caused by diffraction?

Answer 19

Diffraction can cause problems when using optical instruments like microscopes and telescopes. When light enters the instrument it passes through a small gap and diffracts a little. This can lead to a blurry image or loss of detail.