TOPIC 6: Waves

Question 1

How can wave motion be shown with a spring?

Answer 1

Hold one end of the horizontal spring in a fixed position and move the other end up and down

Question 2

How can wave motion be shown in water?

Answer 2

A cork floating on the surface of the water will bob up and down as the wave passes

Question 3

What are waves?

Answer 3

Waves are vibrations (oscillations) that transfer energy from place to place

Question 4

Transverse wave:

Answer 4

• The vibrations are perpendicular to the direction of the energy transfer
• This wave causes the medium’s particles to vibrate in right angles from the wave’s motion
• Examples: waves in water, wave on a spring

Question 5

Longitudinal wave:

Answer 5

• The vibrations are parallel to the direction of energy transfer
• This wave causes the medium’s particles to vibrate in the same direction as the wave’s motion
• Examples: sound waves, pushing a spring in an out

Question 6

What is the amplitude of a wave?

Answer 6

The largest distance that a point on the wave moves from its rest position

Question 7

What is the wavelength of a wave?

Answer 7

The distance between two adjacent wavefronts

Question 8

Required Practical - Ripple Tank:

Answer 8

1) Set up the apparatus
2) Adjust the height of the wooden rod so that it touches the surface of the water
3) Switch on the lamp and motor and adjust until low frequency waves can be clearly observed
4) Measure the length of a number of waves then divide by the number of waves to record wavelength. This can be done by taking a photo for accuracy.
5) Count the number of waves passing a point in ten seconds and divide by ten to determine frequency

Question 9

Sound is a longditudinal wave. Because of this, it can be:

Answer 9

• absorbed
• reflected
• refracted
• transmitted

Question 10

From a long distance, why may someone appear to hit two things together before you hear the sound?

Answer 10

• The speed of light is faster than the speed of sound
• So, the light waves reach your eyes before the sound waves reach your ears

Question 11

Sound waves:

Answer 11

• Are longitudinal waves
• Are produced by the vibration of particles in a medium
• Travel in a series of compressions and rarefractions

Question 12

Angle of incidence =

Answer 12

the angle of reflection

Question 13

What are the seven types of electromagnetic waves? (lowest frequency to highest)

Answer 13

Radiowave
Microwave
Infrared
Ultraviolet (UV)
X-ray
Gamma

Question 14

Electromagnetic waves:

Answer 14

• Electromagnetic waves are transverse waves that transfer energy from the source of the waves to an absorber
• All types of electromagnetic waves travel at the same velocity

Question 15

How does the wavelength change through the electromagnetic spectrum?

Answer 15

The lower the frequency, the longer the wavelength.
Radio waves (which have the lowest frequency) have the longest wavelength and this is the opposite for Gamma rays

Question 16

Gamma rays uses:

Answer 16

• medical imaging and therapy
• gamma rays carry the most energy so we can use them to destroy bacteria and tumours.

Question 17

Gamma rays risks:

Answer 17

Gamma rays are extremely penetrating and damaging to living tissues and cells

Question 18

X-ray safety precautions:

Answer 18

• X-rays are dangerous so we should keep exposure at a minimum
• People working with X-ray equipment should shield themselves

Question 19

How does an X-ray work?

Answer 19

• X-rays penetrate soft materials (like body tissue)
• Bones are dense materials that absorb X-rays. So we can use X-rays to build a shaded image of bones and body tissue

Question 20

X-ray uses:

Answer 20

• Low-energy X-rays are used for medical and industrial imaging
• High-energy X-rays are used to treat cancer
• Security purposes (detecting weapons in airports)

Question 21

X-ray risks:

Answer 21

X-rays are highly ionising (can damage body cells)

Question 22

Ultraviolet uses:

Answer 22

• Energy efficient lamps - UV photons give energy to atoms which then release visible light
• Sun tanning - UV gives energy to skin cells which then change colour

Question 23

Ultraviolet risks:

Answer 23

Exposure to too much UV light can cause skin burns and cancer

Question 24

Infrared uses:

Answer 24

• electrical heaters
• cooking food - the frequency is high enough to give energy to particles in food, increasing their temperature
• infrared cameras - can detect a range of frequencies which are shown in different colours to depict images

Question 25

Infrared risks:

Answer 25

Can cause serious skin burns if emitted from sources of high intensity

Question 26

Microwave uses:

Answer 26

- cooking food - microwaves are absorbed by water, heating it up in the process - makes it useful for cooking food as food contains lots of water - satellite communications - microwaves have a high enough frequency to penetrate the Earth's atmosphere and to reach satellites

Question 27

Microwave risks:

Answer 27

As humans are made up of mostly water, microwaves can be harmful

Question 28

Radiowaves uses:

Answer 28

- television and radio - radiowaves have long wavelengths so, they can be transmitted around the Earth's surface without interference

Question 29

Radio waves risks:

Answer 29

At high intensities, can cause internal heating of living tissue

Question 30

Production of electromagnetic radiation:

Answer 30

electrical circuits - oscillations can produce radio waves. When absorbed, they may create an alternating current with the same frequency as the radio wave itself, so radio waves themselves can lead to oscillations in electrical circuits. changes in atoms and the nuclei of atoms - can result in electromagnetic waves being generated or absorbed over a wide frequency range. Gamma rays originate from changes in the nucleus of an atom.