[P6] Waves

What is a transverse wave?

Transverse waves oscillate perpendicular to the direction of energy transfer

What is a longitudinal wave?

Longitudinal waves osciallate parallel to the direction of energy transfer

What is an example of a transverse wave?

Water waves (ripples)

What is an example of a longitudinal wave?

Sound waves

What is the difference between longitudinal and transverse waves?

Longitudinal waves osciallate parallel to the direction of energy transfer. Transverse waves oscillate perpendicular to the direction of energy transfer.

Are water ripples examples of a transverse or a longitudinal wave?

Transverse

Is sound an example of a transverse or a longitudinal wave?

Longitudinal

What is the definition for the amplitude of a wave?

the maximum displacement of a point on a wave away from its undisturbed position

What is the definition for the wavelength of a wave?

the distance from a point on one wave to the same point on the next wave

What is the definition for the frequency of a wave?

the number of waves passing a point each second

What is the definition for the time period of a wave?

the time taken for a wave to complete one full oscillation

What is the equation that links time period and frequency of a wave?

Period = 1 ÷ frequency

What is the unit for time period?

seconds, s

What is the unit for frequency?

Hertz, Hz

What is the equation that links wave speed, wavelength, and frequency of a wave?

wave speed = frequency x wavelength

What is the unit for wave speed?

metres per second, m/s

What is the unit for wavelength?

metres, m

Describe a method to measure the speed of sound waves in air

Make a loud noise on a field near a wall, and use: a measuring tape to measure the distance to and from the wall; and a stopwatch to measure the time for the echo of the noise to be heard. Use the equation speed = distance ÷ time to calculate the speed

Describe a method to measure the speed of ripples on water

Set up a ripple tank and use: a ruler to measure wavelength; and a stopwatch to measure frequency. Use the equation wave speed = frequency x wavelength to calculate the speed

What is the law of reflection?

The angle of incidence is equal to the angle of reflection

How are echoes formed?

By the reflection of sound waves

How is specular reflection produced?

Waves are reflected from a smooth, flat surface

How is diffucse reflection produced?

Waves are reflected from a rough surface and bounce in many directions

What part of the ear vibrates to the same frequency of incoming sound waves?

Ear drum

What is the range of normal human hearing?

20 Hz to 20 kHz

What are ultrasound waves?

Waves that have a frequency higher than the upper limit for human hearing - above 20,000 Hertz (Hz)

How are ultrasounds used?

breaking kidney stones, cleaning jewellery and medical imaging

What are seismic waves?

Shock waves travelling through the Earth, usually caused by an earthquake

What are seismic P-waves?

Longitudinal seismic waves

What are seismic S-waves?

Transverse seismic waves

What type of seismic wave is faster?

P-waves

What type of materials can P-waves travel through?

Solids and liquids

What type of materials can S-waves travel through?

Solids only

What state is the Earth's outer core?

Liquid

What state is the Earth's inner core?

Solid

What are the different layers of the Earth?

Inner core, outer core, mantle and crust

What are electromagnetic waves?

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

What are the waves on the electromagnetic specturm, in order from longest to shortest wavelength?

Radio, Microwaves, Infrared, Visible light, Ultraviolet, X-rays, Gamma waves.

Which part of the electromagnetic spectrum transfers the most energy?

Gamma rays

Which part of the electromagnetic spectrum has the shortest wavelength?

Gamma rays

Which part of the electromagnetic spectrum has the highest frequency?

Gamma rays

Which part of the electromagnetic spectrum has the longest wavelength?

Radio waves

Which part of the electromagnetic spectrum has the smallest frequency?

Radio waves

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] What happens to a light ray when it enters an object that is more optically dense?

It bends towards towards the normal

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] What happens to a light ray when it enters an object that is less optically dense?

It bends towards away from the normal

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] What causes refraction of waves?

the difference in the velocity of the waves in different substances

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] What four possibilities could happen when a wave goes through a substance?

different substances may absorb, transmit, refract or reflect electromagnetic waves in ways that vary with wavelength

What happens when a wave refracts?

It changes direction

What type of surfaces are good at absorbing and emitting raditation?

Dark, matte (dull) coloured surfaces

What type of surfaces are good at reflecting radition?

Bright, shiny coloured surfaces

Explain why refraction takes place as a wave moves from one substance to another

Refraction takes place because waves will travel at different velocities in different substances

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] How can radio waves be produced?

by oscillations within electric circuits

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] What happens when radio waves are absorbed by an electrical conductor?

they create an alternating current with the same frequency as the radio wave itself

How can gamma rays be produced?

by changes in the nucleus of an atom

Which types of waves can have hazardous effects on body tissue?

ultraviolet waves, X-rays and gamma rays

What is radiation does (in Sieverts) a measure of?

the risk of harm resulting from an exposure of the body to the radiation

What are the risks of ultraviolet waves on body tissue?

they can cause skin to age prematurely and increase the risk of skin cancer

What are the risks of X-rays and gamma rays on body tissue?

they are ionising radiation that can cause the mutation of genes and cancer

What are uses of radio waves?

Television and radio

What are uses of microwaves?

Satellite communications, cooking food

What are uses of infrared?

Electrical heaters, cooking food, infrared cameras

What are uses of visible light?

Fibre optic communications

What are uses of ultraviolet?

Energy efficient lamps, sun tanning

What are uses of X-rays?

medical imaging and treatments (e.g. treating cancer)

What are uses of gamma rays?

medical imaging and treatments (e.g. treating cancer)

What type of image will a convex lens produce?

Real or virtual

What type of image will a concave lens produce?

Always virtual

What is the focal length?

The distance from the lens to the principal focus

How do colour filters work?

They absorb certain wavelengths (and colour) and transmit other wavelengths (and colour).

What is a real image?

An image that is formed where the rays of light are focused

What is a virtual image?

An image that appears to come from behind the lens.

What colour of visible light has the greatest frequency?

Violet

What colour of visible light has the greatest wavelength?

Red

What are the components of white light?

All frequencies of visible colour

How is light transmitted through transparent materials?

Most is transmitted with very little absorption (see through)

How is light transmitted through translucent materials?

Some light is transmitted but not all (partially see through)

How is light transmitted through opaque materials?

All light is reflected or absorbed (not see through)

Why are stars considered to be black bodies?

They are very good emitters of most wavelengths in the electromagnetic spectrum

What happens to the amount of infrared radiation emitted when an object is hotter?

The amount of infrared radiation emitted increases

What is a black body radiator?

An object that absorbs all of the radiation incident on it; it does not reflect or transmit any radiation

What is the relationship between emitted and absorbed radiation for a body at constant temperature?

It is absorbing radiation at the same rate as it is emitting radiation

How does the temperture of a body increase?

When the body absorbs radiation faster than it emits radiation