Topic 6 - Waves

Question 1

What are waves?

Answer 1

Waves transfer energy from one pack to another without transferring matter.

Question 2

How can wave motion be shown?

Answer 2

They can be shown by the vibrations of a spring or by water waves.

Question 3

How can wave motion be shown in waves?

Answer 3

When a wave travels along the surface of water, a cork floating on the surface of the water will only move up and down as the wave passes.

Question 4

How can wave motion be shown in springs?

Answer 4

Hold one end of a horizontal spring in a fixed position and move the other end of the spring up and down. We can observe a wave moving from the end we are holding towards the fixed end of the spring.

Question 5

What is the formula for wave speed?

Answer 5

Wave speed = frequency x wavelength

Question 6

What is the unit for wave speed?

Answer 6

Metres per second (m/s).

Question 7

What is a transverse wave?

Answer 7

Transverse waves cause the particles in the medium (the substance that the wave travels through) to vibrate at right angles (perpendicular) to the direction of the wave’s motion.

Question 8

What are examples of longitudinal waves?

Answer 8

P-waves - pressure waves created during earthquakes
Pushing and pulling springs - create these waves
Sound waves

Question 9

What is a longitudinal wave?

Answer 9

Longitudinal waves cause the particles to move in the same direction relative to the direction of the longitudinal wave (parallel).

Question 10

What is the frequency of a wave?

Answer 10

The frequency of a wave is the number of times a point on the wave oscillates per second.

Question 11

What is the unit for the frequency of a wave?

Answer 11

Frequency is measured in Hertz (Hz).

Question 12

What is the formula for the frequency of a wave?

Answer 12

Frequency = oscillations / time

Question 13

What is the wavelength?

Answer 13

The wavelength is the distance between two adjacent wavefronts. For transverse waves, this is the distance between two peaks of adjacent waves. Measured in metres.

Question 14

What is the amplitude?

Answer 14

The amplitude of a wave is the largest distance that a point on the wave moves from its rest position.

Question 15

If sound is a longitudinal wave, what can it be?

Answer 15

It can be refracted, reflected, absorbed and transmitted.

Question 16

How can sound travel through solids?

Answer 16

They can travel through solids by causing vibrations in the solid.

Question 17

How is sound produced?

Answer 17

Sound is produced by the vibrations of particles in a medium, the vibrations mean that sound waves travel in a series of compressions (where the medium is squashed together) and rarefractions (where the medium is stretched apart).

Question 18

How is the speed of sound measured in the echo experiment from Person 1’s perspective?

Answer 18

Two people stand a measured distance from a tall vertical wall. This distance should ideally be about 100 metres. The first person bangs two wooden blocks together to make a sharp sound and repeats this every time the echo is heard.

Question 19

How is the speed of sound measured in the echo experiment from Person 2’s perspective?

Answer 19

Starting counting from zero, the second person uses a stopwatch to measure the time taken for a number of claps. In the time between two successive claps, the sound travels to the wall and back.

Question 20

How is the speed of sound calculated?

Answer 20

Speed of sound = distance to wall x 2 x number of claps (n) / time taken for n claps.

Question 21

What are electromagnetic waves?

Answer 21

They are transverse waves that travel at the same speed in a vacuum.

Question 22

What can we assume about the speed of electromagnetic waves?

Answer 22

It is the same speed in the air and when in a vacuum.

Question 23

What is the electromagnetic specturm?

Answer 23

It can be split into seven types of wave.

Question 24

What waves are in the EM spectrum ordered from high to low frequency?

Answer 24

Gamma, x-rays, ultraviolet, visible, infrared, microwave and radio waves.