Waves

Question 1

What do waves transmit?

Answer 1

Waves transfer energy from one place to another away from the source without any net movement of matter.

Question 2

What is a Longitudinal wave?

Answer 2

In longitudinal waves the vibrations run parallel to the direction of every transfer.

Question 3

What is a Transverse wave?

Answer 3

In a Transverse waves the vibrations run at right angles to the direction of energy transfer.

Question 4

What is a Progressive wave?

Answer 4

A wave that moves away from a source, transferring energy.

Question 5

How do particles move on a transverse wave?

Answer 5

The particles oscillate vertically to create the wave movement, but they don’t move forwards or backwards - despite the wave doing so.

Question 6

Define Wavelength:

Answer 6

λ (in Meters) is the distance between two successive points on the same wave. (Length of one whole wave cycle).

Question 7

Define Period:

Answer 7

(In seconds) Is the time it takes for one complete pattern of oscillation to take place.

Question 8

Define Frequency:

Answer 8

(in Hertz, Hz) Is the number of oscillations per unit time (seconds) passing a given point.

Question 9

Define Displacement:

Answer 9

x (measured in Meters) is the displacement. It is the distance any part of the wave has moved from its mean (rest) position. It can be positive or negative.

Question 10

Define Amplitude:

Answer 10

A, meters is the maximum magnitude of displacement.

Question 11

Phase Difference:

Answer 11

p, rad (or radian) how much one wave ‘lags’ behind another.

Question 12

Formula for wave speed:

Answer 12

v = f x λ. v = velocity, f = frequency, λ = wavelength.

Question 13

Define Intensity:

Answer 13

Intensity is energy transferred per m2. Measured in Wm-2

Question 14

Formula for Intensity:

Answer 14

(energy/time) / area or power / area.

Question 15

If power spreads out equally in all directions:

Answer 15

power / 4π x r2.

Question 16

What is the inverse of the period?

Answer 16

Frequency. f = 1/t.

Question 17

What is the displayed wave on an oscilloscope called?

Answer 17

A trace.

Question 18

What are the squares on an oscilloscope called?

Answer 18

Divisions.

Question 19

What does the vertical axis represent?

Answer 19

Volts. Volts/div is controlled by GAIN knob.

Question 20

What does the horizontal axis represent?

Answer 20

Seconds. Sec/div controlled by timebase knob.

Question 21

How could you calculate frequency on an oscilloscope?

Answer 21

Calculate the period on the wave by finding how many squares wide points A to B are.

Multiply squares by timebase setting.

Use f=1/t to find answer.

Question 22

What are the two ways a transverse wave can be shown?

Answer 22

• Graphs of Displacement against distance along the path of the wave.
• Graphs of Displacement against time.

Question 23

What do longitudinal waves consist of?

Answer 23

Compressions and Refractions.

Question 24

What is the relationship between Intensity and Amplitude?

Answer 24

Intensity ∝ (Amplitude)^2

Question 25

If the Intensity of a source is quadrupled, what happens to the amplitude?

Answer 25

It doubles.

Question 26

What is the speed of EM waves in a Vacuum?

Answer 26

3.00x10^8 (Slower in other media).

Question 27

What are EM waves?

Answer 27

EM waves are transverse waves consisting of vibrating electric and magnetic fields at right angles to each other and to the direction of travel.

Question 28

What can all EM waves do?

Answer 28

Like all waves, they can be: Refracted, Diffracted, Reflected and undergo interference. Also obey v = f x λ. They also carry energy, like all progressive waves.
They can also be polarised like all transverse waves.

Question 29

What is the relationship between frequency and energy?

Answer 29

Energy is directly proportional to frequency. So Gamma Waves have highest energy and radio waves the lowest.