Chapter 6: Waves

Sound waves

________ are caused by vibrating objects.

Radiographers

________ use X- rays and gamma rays to treat people with cancer.

Lenses

________ form image by refracting light and changing its direction.

Radio waves

________ are made by oscillating charges.

Ultrasound

________ can also be used to find flaws in objects such as pipes or materials such as wood or metal.

Ultraviolet radiation

________ is produced by the sun, and exposure to it is what gives people a suntan.

slight time delay

There is a(n) ________ between the signal being sent and received because of the long distance the signal has to travel.

Refraction

________- waves changing direction at a boundary.

oscillate

When waves travel through a medium, the particles of the medium ________ and transfer energy between each other.

energy

The ________ carried by the waves is transferred to the electrons in the material of the receiver.

currents

Alternating ________ are made up of oscillating charges.

Echoes

________ are just reflected sound waves.

signal generator

Using a(n) ________ attached to the dipper of a ripple tank you can create water waves at a set frequency.

CT

A(n) ________ scan uses X- rays and a computer to build up a picture of the inside of a patients body.

Frequency

________ is the number if complete waves passing a certain point per second.

time of day

Medium- wave signal can slo reflect from the ionosphere, depending on atmospheric conditions and the ________.

ultrasound imaging

It can be completely reflected or partially reflected (like in ________)

focal length

The object being magnified must be closer to the lens than the ________.

Security pens

________ can be used to mark property with you name, under UV light the ink will glow, but its invisible otherwise.

principal focus

It causes rays of light parallel to the axis to be brought together at the ________.

Risk

________ can be different for different parts of the body.

incident ray thats

The ________ parallel to the axis is refracted through the principal focus on the other side of the lens.

point of incidence

The normal is an imaginary line thats perpendicular to the surface at the ________.

X rays

________ and gamma rays are types of ionising radiation.

incident ray

A(n) ________ passing through the centre of the lens carries on in the same direction.

atmosphere

If the ________ starts to absorb more radiation without emitting the same amount, the overall temperature will rise until absorption and emission are equal again.

Earthquakes

________ and explosions cause seismic waves.

White objects

________ reflect all of the wavelengths of visible light equally.

Gamma radiation

________ can also be used as a medical tracer- this is where a gamma- emitting source is injected into the patient, and its progress is followed around the body.

EM waves

All ________ are transverse waves that transfer energy from a source to an absorber.

IR radiation

Food can be cooked using ________, the temperature of the food increases when it absorbs ________.

perfect black body

A(n) ________ is an object that absorbs all of the radiation that hits it.

High frequency waves

________ like UV, X- rays and gamma rays all transfer lots of energy and so can cause lots of damage.

Specular reflection

________ happens when a wave is reflected in a single direction by a smooth surface.

Electrical devices

________ can be made which produce electrical oscillations over a range of frequencies.

Waves

________ can be used to detect and explore.

white light

If ________ is shone at a blue colour filter, only blue light will be let through.

translucent objects

Some wavelengths of light may be absorbed or reflected by transparent and ________.

Longitudinal waves

________ have parallel vibrations.

angle of incidence

The angle between the rau and the normal is the ________.

local temperature

At night, less radiation is being absorbed than is being emitted, causing a decrease in the ________.

rough surface

When light is reflected by a(n) ________, the surface appears matte and you dont get a clear refection of objects.

effects of each type of radiation

The ________ are based on how much energy the wave transfers.

Radiation dose

________ is a measure of the risk of harm from the body being exposed to radiation.

From the frequency, you can find the period of a wave using

T=1/f

Refraction

waves changing direction at a boundary

When a wave crosses a boundary between materials at an angle it changes direction

its refracted

When EM radiation enters living tissue-like you

its often harmless, but sometimes it creates havoc

The principal focus of a concave lens is the point where rays hitting the lens parallel to the axis appear to all come from

you can trace them back until they all appear to meet up at a point behind the lens

When you look in a mirror you see a virtual image of your face

because the object appears to be behind the mirror

To describe an image you need to say

how big it is compared to the object, whether its upright or inverted relative to the object, whether its real or virtual

The only colours you cant make by mixing are the primary colours

pure red, green and blue