P6 - Waves

Question 1

What are transverse and longitudinal waves

Answer 1

Transverse - oscillations that are perpendicular to energy transfer
Longitudinal - oscillations that are parallel to energy transfer

Question 2

Give examples of transverse and longitudinal waves

Answer 2

Longitudinal waves - sound waves
Transverse waves - electromagnetic waves, ripples and waves in water, wave on a string

Question 3

Describe what is meant by:
amplitude
wavelength
frequency

Answer 3

The amplitude of a wave is the maximum displacement of a point on a wave away from its undisturbed position.
The wavelength of a wave is the distance from a point on one wave to the equivalent point on the adjacent wave.
The frequency of a wave is the number of waves passing a point each second.

Question 4

What do you measure the speed of sound

Answer 4

Oscilloscope

Question 5

Describe how to measure the speed of water ripples using a ripple tank ( 6 marks)

Answer 5

Using a signal generator attached to the dipper of a ripple tank - create water waves at a set frequency
Dim the lights in the lab and turn on the lamp - wave crests as shadows appear below the tank
Distance between each shadow line is equal to one wavelength
Measure distance between 10 shadow lines then divide this by 10 - average wavelength
Use v=fw

Question 6

What is the equation for period

Answer 6

1/f

Question 7

Describe how the wave equation can be used for waves on strings (6 marks)

Answer 7

Turn on signal generator and vibration transducer - string will start to vibrate
Adjust the frequency of the signal generator until there’s a clear wave on the string
Frequency needed depends on the length of the string between pulley and transducer and masses used
Measure the wave length of these waves - 5 in one go - divide by 5 - mean half-wavelength
Double to get full wavelength
Frequency is what the signal generator is set to
Substitute to find speed using v=fw

Question 8

What are electromagnetic waves (2 marks)

Answer 8

Electromagnetic waves are transverse waves that transfer energy from the source of the waves to an absorber.

Question 9

How is the electromagnetic spectrum grouped

Answer 9

Going from long to short wavelength (or from low to high frequency)

Question 10

Name all parts of the magnetic spectrum

Answer 10

ROMANIAN MEN IN VENEZUELA USING EXPENSIVE GUNS !
Radio waves - micro waves - infrared - visible light - ultra violet - x rays - gamma rays

Question 11

What part of the electromagnetic spectrum can humans see

Answer 11

visible light fr.

Question 12

What three things can all waves do

Answer 12

Absorbed
Transmitted
Reflected

Question 13

What causes refraction

Answer 13

difference in velocity of the waves in different substances

Question 14

What is bigger the angle of incidence or angle of refraction

Answer 14

angle of incidence

Question 15

If the wave fonts are closer together what does it mean ( 2 marks)

Answer 15

Shows a change in wavelength and change in velocity

Question 16

investigate how the amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface ( 6 marks obvs)

Answer 16

Place an empty Leslie cube on a heat proof mat
Boil water in a kettle and fill Leslie cube
Wait for cube to warm up - hold thermometer against each of the four faces of the cube - (should be same temperature)
Hold an infrared detector 10 cm away from one of the cube’s vertical faces and record amount of IR radiation it detects
Repeat for each cube’s vertical face - position the detector at the same distance from the cube each time
More infrared radiation from the black surface than white
More from matt surfaces from shiny
Repeat experiment more than once

Question 17

How can radio waves be produced

Answer 17

Radio waves can be produced by oscillations in electrical
circuits.

Question 18

How can radio waves be produced

Answer 18

Radio waves can be produced by oscillations in electrical
circuits.

Question 19

What are the hazards from ultraviolet and x rays

Answer 19

UV - Premature ageing of the skin and increase risk of skin cancer
X-rays - Ionising radiation that can cause mutations of genes and cancer

Question 20

What are the uses of:
radio waves
microwaves
infrared

Answer 20

radio waves – television and radio
* microwaves – satellite communications, cooking food
* infrared – electrical heaters, cooking food, infrared cameras