Waves

Question 1

What is the difference between a transverse and longitudinal wave?

Answer 1

Transverse: vibrates perpendicualr to the direction of energy travel (don’t always require a medium)
Longitudinal: vibrates parallel to the direction of energy travel. (always requires a medium)

remember WAVES travel, not the water or air)

Question 2

How does one calculate frequency?

Answer 2

frequency = number of oscilations / time
or
frequency = 1 / period

Question 3

What is a wave’s period?

Answer 3

The time taken for the wave to complete one oscilation

Question 4

What is amplitude?

Answer 4

The largest distance the wave moves from its centre/rest position.

Question 5

Recite two of the wave speed equations.

Answer 5

wave speed (m/s) = distance (m) / time (s)

wave speed (m/s) = frequency (Hz) x wavelength (m)

Question 6

Features of sound waves

Answer 6

• longitudinal waves
• vibrations as a series of compressions (where the particles are close together) and rarefactions (where they are more spread out)
• travels at 343m/s in dry air.

Question 7

What are seismic waves?

Answer 7

A wave that travels through the earth
They can either be:
P-waves (pressure waves): Longitudinal, faster, can pass through solids and liquids, but travel through solids faster
or S-waves (secondary waves): Transverse, can only travel through solids.

Question 8

What is the frequency?

Answer 8

Number of waves per second. Measured in Hz.

Question 9

What are 2 problems with the sound wave practical and how do we fix them?

Answer 9

1: Reaction time
The person holding the timer may have a poor reaction time. We can solve this by increacing the number of people timing and calculating the avergae from their results.

2: The time between the clash and hearing it is too short
Increace the distance between the person timing and the cymbals.

Question 10

How does one calculate the wavelength in the waves in a solid core practical

Answer 10

2 ( length / number of half wavelengths )

Question 11

How would one work out the distance an ultrasound has travelled?

Answer 11

distance = speed x time

then divide your answer by two (as without dividing it would give you the distance to and back again)

Question 12

What is the speed of an ultrasound in water?

Answer 12

1600 m/s

Question 13

Why can ultrasounds be used to see images?

Answer 13

It partially reflects at the boundry between two different densities

Question 14

How can a change in an atom cause electromagnetic radiation?

Answer 14

• Electrons gain energy and move to a higher energy level away from the nucleus
• When the electron returns to its original energy level, it generates an electromagnetic wave

Question 15

How are radio waves produced?

Answer 15

• When electrons ocillate in electrical circuts
• They can be aborbed, e.g, by an aerial
• They cause electrons in the circut of the aerial to oscillate at the same frequency as the radio waves