Waves

What are the two types of waves?

1. Transverse
2. Longitudinal

What is a transverse wave?

A wave for which the oscillations are perpendicular to the direction of energy transfer.

What is a longitudinal wave?

A wave for which the oscillations are parallel to the direction of energy transfer.

Give two examples of transverse waves.

1. Electromagnetic waves
2. Seismic s-waves

Give two examples of longitudinal waves.

1. Sound waves
2. Seismic p-waves

What are the two parts of a longitudinal wave called?

Compressions and rarefactions.

What is a wave’s amplitude?

The maximum displacement of a point on a wave from its undisturbed position.

What is wavelength?

● The distance from a point on a wave to the same position on the adjacent wave

● Most commonly peak to peak or trough to trough

What is the frequency of a wave?

The number of waves that pass a given point each second.

What is the unit used for frequency?

Hertz, Hz

What is wave speed?

The speed at which the wave moves or at which energy is transferred through a medium.

What does a wave transfer?

Energy

State the equation used to calculate wave speed. Give appropriate units

Wave Speed = Frequency x Wavelength Speed (m/s), Frequency (Hz), Wavelength (m)

What word is used to describe when a wave bounces off a surface?

Reflection

How do sound waves travel through a solid?

The particles in the solid vibrate and transfer kinetic energy through the material.

What is the frequency range of human hearing?

20 Hz - 20kHz (1kHz = 1000 Hz)

What are ultrasound waves?

Waves which have a frequency higher than the upper limit of human hearing (20kHz).

Give an example use for ultrasound waves?

Medical or industrial imaging

What natural event causes seismic waves to be produced? What types are

produced?

● Earthquakes

● They produce both P-waves and S-waves

State a difference between the mediums that P-waves and S-waves can travel

through.

● P-waves travel through both solids and liquids

● S-waves only travel through solids (not liquids)

What technique is used to detect objects in deep water and measure water depth?

● Echo sounding

● High frequency sound waves are emitted, reflected and detected

● Time difference between emission and detection, alongside wave speed, are used to calculate distances

What type of spectrum do electromagnetic waves form?

A continuous spectrum.

Order the types of electromagnetic radiation from lowest to highest

frequency.

● Radio waves

● Microwaves

● Infrared

● Visible Light

● Ultraviolet

● X-rays

● Gamma Rays

How do the speeds of EM radiation differ in a vacuum and in air?

Electromagnetic waves all travel at the same speed in a vacuum and in air.

What property of waves in different mediums causes refraction?

● Velocity

● Wave speed is slower in denser materials, causing refraction

In which direction (relative to the normal) do waves refract when entering a denser

medium?

● They bend towards the normal

● The angle of refraction is less than the angle of incidence

What type of waves can be produced by oscillations in an electrical circuit?

radio waves

How can radio waves create an alternating current in a circuit?

When radio waves are absorbed, they can induce oscillations in a circuit with the same frequency as the waves themselves

Where do gamma rays originate from?

They originate from changes in the nuclei of atoms

What health effects can ultraviolet waves cause?

● They can cause the skin to age prematurely

● The can increase the risk of developing skin cancer

What health effects can X-rays and Gamma rays

cause?

● They are ionising radiation so can cause mutations in genes

● They can lead to increased risk of developing various cancers

Give three practical uses for infrared radiation.

1. Electrical heaters
2. Cooking food
3. Infrared cameras

Give two practical uses for microwave radiation.

1. Satellite communications
2. Cooking food

Give two practical uses for radio wave

. Television transmission


2. Radio transmission

What wave phenomenon is used by lenses to form an image?

refraction

How does a convex lens form an image

Parallel rays of light are refracted and brought together at a point known as the principal focus.

What is meant by the focal length of a lens?

The distance from the lens to the principal focus.

What is the difference between the

image produced by a convex and a concave lens?

● Convex lenses can produce real or virtual images

● Concave lenses can only produce virtual images

Why does magnification not have a unit?

● It is the ratio between image height and object height

● Ratios do not require units

What symbol is used to represent a convex lens in a ray diagram?

What symbol is used to represent a concave lens in a ray diagram?

What determines the colour of visible light waves?

The wavelength and frequency of the light waves.

What colour of visible light has the highest frequency?

Blue

What colour of visible light has the largest wavelength?

Red

What is meant by the term ‘specular reflection’?

Reflection from a smooth surface in a single direction.

What is meant by the term ‘diffuse reflection’?

Reflection from a rough surface which causes scattering.

How does a red colour filter work?

● A red filter absorbs all wavelengths of light other than those in the red range of the spectrum

● This means only red light passes through the filter

What determines the colour of an opaque object?

● Different objects reflect different wavelengths of light by different amounts

● The wavelengths that are most

strongly reflected determine the colour

What happens to the wavelengths of

light that aren’t reflected by an opaque object?

Any wavelengths that aren’t reflected are absorbed by the object.

What colour does an object appear if all

wavelengths are reflected by equal amounts?

White

What colour does an object appear if all wavelengths are absorbed?

black

What do all bodies (objects) emit and absorb?

infrared radiation

What happens to the quantity of infrared radiation emitted by an object as

temperature increases?

The hotter the object, the more infrared radiation it will emit.

What is a perfect black body?

An object that absorbs all of the radiation that is incident upon it.

How much radiation does a perfect black body reflect or transmit?

none

Why is a perfect black body the best possible emitter of radiation?

● It is a perfect absorber since it absorbs all radiation incident on it

● A perfect absorber is also a perfect emitter

Other than the intensity of radiation

emitted, how does increasing the temperature of an object affect its emissions?

The wavelength distribution of any emission is dependent on the object’s temperature.

What can be said about the rates of emission and absorption for a body at

constant temperature?

The body is absorbing and emitting radiation at the same rate.

What can be said about the rates of emission and absorption for a body

increasing in temperature?

The body is absorbing radiation faster than it is emitting it

Give two factors that affect the temperature of the Earth

1. The Earth’s rate of absorption and emission of radiation
2. The amount of reflection of radiation into space