Wave properties levels 7-9

Question 1

In a longitudinal wave, what is a compression and what is a rarefaction.

Answer 1

A compression is an area where the particles are close together

A rarefaction is an area on a wave where the particles are far apart

Question 2

What is the main difference between the nature of a mechanical wave and an electromagnetic wave

Answer 2

A mechanical wave is made of oscillating (vibrating) particles. An electromagnetic wave is made of oscillating electric and magnetic fields.

Question 3

Explain how you would combine the period equation and the wave speed equation to solve this problem:

What is the speed of a wave with a period of 10 seconds and a wavength of 8m?

Answer 3

1. First use the period equation to find the frequency

frequency = 1/period

= 1/10

= 0.1Hz

2. then use the wave speed equation to calculate the wave speed

speed = frequency x wavelength

= 0.1 x 8

= 0.8 m/s

Question 4

Describe why

1) a wave will bend towards the normal when it moves into a more optically dense medium
2) a wave will bend away from the normal when it moves intor a less optially dense medium

Answer 4

1) when the wave moves into a more optically dense medium the wave does not move as fast. this causes the wavelength of the wave to shorten and bunches up the wave. The slower moving wave will effectively ‘drag round’ the rest of the wave, resulting in a bend towards the normal
2) When the wave moves into a less optically dense medium it bends away from the normal. This happens becuase the wave moves faster and this causes the wavelengths to spread out. This has the effect of pushing the wave round so it bends away from the normal.

Question 5

What are the potential sources of error when measuring the speed of sound?

Answer 5

The expeirment could give any value from a range of speeds of sound. This is becuase the level of moisture in the air will affect the speed of sound. If the air is more dry then the speed of sound will be slower than if the air is moist. This is a problem as the experiment is usually performed outside to get the required space

Human error is also an important factor as human reaction time can cause a delay in starting the wave or stopping the timer, and the error in reaction time can be just as large as the actual time you are trying to measure, leading to large errors