GCSE Physics- Waves

How does a lense form an image?

Refracting light

How do convex lenses work?

Parallel rays of light are brought to a focus at the principal focus.

What are ray diagrams used for?

To show the formation of images by convex and concave lenses

What types of image is produced by a convex lense?

Real or virtual

What types of image is produced by a convex lense?

Always virtual

How are convex lenses represented in a ray diagram?

An arrow with points on either side facing outwards

How are concave lenses represented in a ray diagram?

An arrow with points on either side facing inwards

Why is each colour within the visible light spectrum distinct?

Each one has its own narrow band of wavelength and frequency

What is specular reflection?

Reflection from a smooth surface in a single direction

What is diffuse reflection?

Reflection from a rough surface causes scattering

How do colour filters work?

They absorb certain wavelengths and colour and transmit other wavelengths and colur

How is the colour of an opaque object determined?

-By which wavelengths of light are more strongly reflected

-Wavelengths that are not reflected are absorbed

-If all wavelengths are reflected equally the object appears white

-If all wavelengths are absorbed the objects appears black

What are objects that transmit light called?

Transparent/translucent

What is a perfect black body?

-An object that absorbs all of the radiation incident on it

-A black body does not reflect or transmit any radiation

-Since a good absorber is also a good emitter, a perfect black body would be the best possible emitter.

What is the correlation between temperature and infrared radiation?

The hotter the body, the more infrared radiation it radiates in a given time

Why does the temperature of the body increase?

-A body at constant temperature is absorbing radiation at the same rate as it is emitting radiation

-The temperature of a body increases when the body absorbs radiation faster than it emits radiation

What does the temperature of the Earth depend on?

-The rates of absorption and emission of radiation

-Reflection of radiation into space

Order of electromagnetic spectrum

-Radiowaves

-Microwaves

-Infrared radiation

-Visible light

-Ultraviolet

-X-ray

-Gamma ray

Radiowave uses

-Radios

-TV stations

Microwave uses

-Microwaves

-Satellites

Infared radiation uses

-Thermal imaging

-Toasters

Visible light uses

-Cameras

-Fireoptics

Ultraviolet uses

-Sunbeds

-Detecting forgery

X-ray uses

-X-rays

-Bombs

Gamma rays uses

-Radiotherapy

-Sterilisation

What are electromagnetic waves?

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

What part of the electromagnetic spectrum has the longest wavelength?

Radio waves

What part of the electromagnetic spectrum has the highest frequency?

Gamma rays

Why does refraction happen?

The difference in velocity of the waves in different substances

How are radio waves produced?

Oscillations in electrical circuits

How do radio waves induce oscillations in an electrical circuit?

When radio waves are absorbed they may create an alternating current with the same frequency as the radio wave itself

What is radiation dose?

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

What do the hazardous affects of UV, X-Rays and Gamma rays depend on?

-Type of radiation

-Size of the dose

What can waves be used for?

-Radio

-Sound

-Microwaves

Wavelength

The distance between two peaks

Amplitude

The maximum displacement of a point of a wave from its rest position

Frequency

Number of waves passing a fixed point every second (Hz)

Transverse waves

Oscilations at right angles to the direction of energy trasnfer

Longitudinal waves

Oscillations parallel to direction of travel

Examples of transverse waves

-Light waves

-Microwaves

-Radio waves

Examples of longitudinal waves

-Sound waves

-Ultrasound waves

-Seismic P Waves

Equation for period of a wave

1/Frequency

What is a period of a wave?

Time taken for each wave to pass a fixed point

How is the period of wave related to its frequency?

As the frequency of a wave increases, the period decreases

What is wave speed?

How far the wave travels every seccond?

Wave speed equation

Frequency x Wavelength

What happens when a wave crosses a boundary between two different materials?

It changes directions

What is a sound wave?

A longitudinal wave that creates sound

Refraction

The wave changes direction when going through something

Reflection

Wave bounces off a surface

Where are waves reflected?

At the boundary between two different materials, they can either be absorbed or transmitted

Why is human hearing limited?

The conversion of sound waves to vibrations of solids works over a limited frequency range

How is sound heard?

Sound waves cause the ear drum and other parts to vibrate which causes the sensation of sound

What is the frequency range of human hearing?

2hx-20kHz

How can the distance away from a boundary be worked out?

The time taken for the reflections to reach a detector

How are ultrasound waves used for medical imaging?

They are partially reflected when they meet a boundary between two different media

-This allows ultrasound waves to be used for both medical and industrial imaging.

What type of waves do earthquakes produce?

Seismic

What are the types of seismic waves?

-P-waves

-S-waves

What are p-waves?

-Longitudinal, seismic waves

-They travel at different speeds through solids and liquids

What are s-waves?

Transverse, seismic waves

-They cannot travel through a liquid

What do seismic waves provide evidence for?

The structure and size of the Earth’s core

How are objects detected in deep water?

Echo sounding using high frequency sound waves

How is water depth measured>

Echo sounding using high frequency sound waves