Waves

Question 1

Longitudinal waves

Answer 1

Movement of particles are parallel to the direction of energy

Question 2

Transverse waves

Answer 2

Movement of particles are perpendicular to the direction of energy

Question 3

Evidence that shows for ripples, it’s the wave that travels and not the water itself

Answer 3

A boat or piece of paper bobs up and down but does not move along with the wave

Question 4

Amplitude

Answer 4

The maximum displacement from the rest line to the peak

Question 5

Wavelength

Answer 5

The distance from a point in one wave to the equivalent point in the adjacent wave

Question 6

Frequency

Answer 6

The number of waves passing a point each second

Question 7

Describe an experiment to determine the speed of sound

Answer 7

1. Two people stand distance of 100m apart measured using a trundle wheel
2. One person has 2 wooden blocks which they bang above their head
3. The second person has a stopwatch which they start when they see the first person bang the blocks and stop when they hear the sound
4. This is then related several times and a mean is calculated
5. The speed of sound is calculated using v=s/t

Question 8

Describe a method to measure the speed of ripples on a water surface

Answer 8

1. Full a rectangular tank with water
2. On one side mark a starting point where the ripples will be generated
3. Gently drop the small floating object into the water at the starting point which will create ripples
4. As soon as the object is dropped start a stopwatch
5. As the ripples expand outward use a rule to measure the distance from the starting point to where the ripples are at a certain point in time
6. Stop the timer when the ripples reach a desired distance
7. Calculate speed using v=s/t
8. Repeat and calculate a mean

Question 9

Ultrasound waves

Answer 9

• Have a higher frequency than the limit of human hearing
• ultrasound waves are partially reflected when they meet a boundary
• the time taken for the reflections to reach a detector can be used to determine how far away such a boundary is
  -> this allows them to be used for medical and industrial imaging

Question 10

Seismic waves

Answer 10

• produced by earthquakes
• p-waves: longitudinal seismic waves that travel at different speeds through solids and liquids
• s-waves: transverse seismic waves that cannot travel through liquid
• p-waves and s-waves produce evidence for the structure and size of the earths core

Question 11

Electromagnetic waves

Answer 11

Transverse waves that transfer energy from the source of the waves to an absorber

Question 12

Order or EM waves from longest wavelength to highest shortest wavelength

Answer 12

• radio
• microwaves
• infrared
• visible light
• ultraviolet
• xrays
• gamma rays

Question 13

Uses of the EM waves

Answer 13

Radio waves - television and radio

Microwaves - satellite communications and food

Infrared - electrical heaters, cooking food and infrared cameras

Visible light - fibre optic communications

Ultraviolet - sun tanning

X-rays and game rays - medical imaging and treatments

Question 14

For a distant object that is placed more than twice the focal length from the lens, the image is…

Answer 14

inverted
diminished
real

Question 15

For an object placed between one and two focal lengths from the lens, the image is:

Answer 15

inverted
magnified
real

Question 16

When the object is placed at a distance less than the focal length. The image is:

Answer 16

upright
magnified
virtual

Question 17

Concave lenses always produce images that are:

Answer 17

upright
diminished
virtual

Question 18

Order the colour spectrum in increasing frequency and decreasing wavelength

Answer 18

red
orange
yellow
green
blue
indigo
violet

Question 19

What can happen to light waves between the boundary of 2 objects

Answer 19

• Waves can be absorbed at the boundary between two different materials. When waves are absorbed by a surface, the energy of the wave is transferred to the particles in the surface. This will usually increase the internal energy of the particles.
• Waves can also be transmitted at the boundary between two different materials. When waves are transmitted, the wave continues through the material. These materials are transparent because light is transmitted with very little absorption. Translucent materials transmit some light but are not completely clear.

Question 20

How do objects appear in white light

Answer 20

When white light shines on an opaque object, some wavelengths or colours of light are absorbed. These wavelengths are not detected by our eyes. The other wavelengths are reflected, and these are detected by our eyes.

Question 21

How do objects appear in coloured light

Answer 21

An object appears to be black if it absorbs all the wavelengths of visible light. For example, an object that appears blue in white light will appear black in red light. This is because the red light contains no blue light for the object to reflect.

Question 22

What is intensity

Answer 22

How much energy is transferred to a given area in a certain amount of time

Question 23

What is distribution of wavelengths

Answer 23

The spread of intensities of different wavelengths

Question 24

Objects temperature link to intensity and distribution

Answer 24

As temp increases the intensity of every emitted wavelength increases

As the temperature of an object increases the peak wavelength decreases

Question 25

Explanation of temp and intensity

Answer 25

A hotter object gives out more energy of every wavelength of radiation than a cooler object

Question 26

Explanation of temp and distribution

Answer 26

As an object gets hotter, the intensity increases more rapidly for shorter wavelengths -> a bigger amount of the radiation emitted by a hot object has a short wavelength compared to that emitted by a cooler object

Question 27

What are sound waves

Answer 27

Longitudinal waves of vibrating particles caused by vibrating objects -> these vibrations are passed through the surrounding matter as a series of compressions and rarefractions

Question 28

What happens when a sound wave enters a denser medium

Answer 28

It speeds up so it’s wavelengths increase

Question 29

How do microphones work

Answer 29

Sound waves cause a diaphragm to vibrate and this movement is converted into an electrical signal

Question 30

Human hearing range

Answer 30

20Hz - 20kHz

Question 31

How ears work

Answer 31

Sound waves of certain frequencies reach your ear drum and make it vibrate -> these vibrations are passed on to ossicles in the ear through canals and to the cochlea -> the cochlea turns these vibrations into electrical signals which get sent to your brain and allow you to hear the sound

Question 32

Properties of ultrasound

Answer 32

When waves pass from one medium into another some of the waves are reflected by the boundary between the 2 media and some of transmitted -> this is **partial reflection**

Question 33

What does partial reflection in an ultrasound mean

Answer 33

You can point a pulse of ultrasound at an object

Question 34

How to measure how far away a boundary is

Answer 34

The time it takes for the reflections to reach a detector

Question 35

Ultrasound in medical imaging

Answer 35

Ultrasound waves can pass through the body but whenever they reach a boundary between 2 different mediums (like fluid in the womb and the skin of the foetus) some of the wave is reflected back and detected

Question 36

Echo sounding

Answer 36

Type of sonar used by boats where high frequency sound waves are used to find out the depth of the water or locate objects -> sound waves are emitted by the boat and then the time taken for the echo to return is measured and then can be used to calculate distance to the object that reflected the sound (if u know the speed of sound in the water)

Question 37

What are ‘body waves’

Answer 37

Waves that travel through the earth, not across its surface

Question 38

What do seismic waves show

Answer 38

- **seismic waves’ paths curve** showing that there is a gradual change in the density of the mantle - **s waves aren’t detected on the opposite side of the earth** showing that the outer core must be liquid - **the existence of shadow zones where no P-waves are detected** suggested the existence of a solid inner core - **kinks in the paths of P-waves travelling to the other side of the earth** suggest a sudden change in the density of the material they are passing through