Wavelength

Question 1

What is a wave?

Answer 1

A wave is something which transfers energy (from one place to another) without a (permanent) motion of the material through which the wave is travelling through.

Question 2

What is a transverse wave?

Answer 2

In a transverse wave, the oscillations (vibrations) are perpendicular to the direction of energy transfer.

Question 3

What is the amplitude?

Answer 3

The maximum displacement of a point on a wave from its undisturbed position (aka crest to equilibrium

Question 4

What is a longitudinal wave?

Answer 4

in a longitudinal wave, the oscillations (vibrations) are parallel to the direction of energy transfer.

Question 5

How do we heaer sound?

Answer 5

The eardrum vibrates when a sound wave hits it.
The vibrations are passed on to the cochlea.
Vibrations are then converted into electrical signals, which travel along the auditory nerve to the brain.

Question 6

What is a stationary/standing wave?

Answer 6

A standing wave is a wave that oscillates in time but whose peak amplitude profile does not move in space (aka has nodes, where there is 0 displacement).

Question 7

What is ultrasound?

Answer 7

Vibrations at a higher frequency than a human ear can detect.

Question 8

What are the uses of ultrasound in medical/prenatal application/industrial application

Answer 8

A transducer produces (and detects) ultrasound waves
Ultrasound waves travel at different speeds through different materials.
Each ultrasound wave pulse is partially reflected from boundaries between different types of tissues (or reflected form boundaries - cracks - in the material for industrial application).
Reflected waves detected by the trasnducer arrive at different times.
A computer builds up an image of internal tissue boundaries. (or cracks)

Question 9

What is a P wave?

Answer 9

A P wave is a primary wave - they’re the first waves to arrive at your earthquake wave detector.
They are longitudinal.
They can travel through both liquid and solid layers on earth.

Question 10

What is an S wave?

Answer 10

Secondary wave.
Slower
Transverse
Can travel through solids
Cannot travel through liquids.

Question 11

What are the main features of seismic waves on the earth?

Answer 11

They travel through the body of the planet
Their direction changes abruptly by refraction, at boundaries
The paths are curved, also by refraction, due to gradually changing density of the rock
S Waves can travel through solids
S-wave shadow zone is the area of the Earth’s surface where S waves are not detected following an earthquake.
There are also P wave shadow zones.

Question 12

What are the properites of the waves in the electromagnetic spectrum?

Answer 12

-all travel at same speed (speed of light) in a vacuum
Can all travel through a vacuum
All waves on EM spectrum are transverse
All waves on EM spectrum can be refracted, reflected and diffracted.

Question 13

What is the order of EM waves, from largest to smallest?

Answer 13

Radiowaves,
Microwaves
Infrared radiation
Visible light
Ultra violet
X rays
Gamma rays

Question 14

What are the different uses of EM waves?

Answer 14

Radiowaves - communications
Microwaves - communication and heating food
Infrared - remote controls, heating things, detect people and fires
Visible light - used to see, measure things and photography
Ultraviolet - sunbeds, kill bacteria and security marketing
x rays - see through things
Gamma rays - medical treatment and sterilsation

Question 15

What is a black body?

Answer 15

A black body is a theoretical object which is a perfect emitter and absorber of EM radiation. No radiation is reflected or transmitted.

Question 16

Give a summary of blackbody radiation distribution graph.

Answer 16

The intensity of all wavelengths increases as the temperature increases
The peak wavelength decreases as temperature increases
Range of wavelengths emitted increase as temperature increases

Question 17

What is the law of relfection of light?

Answer 17

The angle of incidence is equal to the angle of reflection.
The incident ray, normal ray and reflected ray all lie on the same plane.

Question 18

What is the normal?

Answer 18

An imaginary line which is at right angles/perpendicular to a surface.

Question 19

What is refraction and what is it caused by?

Answer 19

Refraction is the bending of a path of a light wave as it encounters a boundary between two transparent materials.
The refraction is caused by a change in the speed of the ray of ligthwhen crossing the boundary (light either speeds up or slows down).
The change of speed of light atthe boundary occurs because different materials have different optical density.

Question 20

What is dispersion and how does it occur?

Answer 20

Dispersion is the breaking up of white light.
Each colour has a different wavelength of light.
Each wavelength is slowed down by a different amount by the prism (blue more than red).
The prism disperses the light.
Shorter wavelengths slow down more so bend towards the normal more sharply.

Question 21

What is a virtual image?

Answer 21

An image which is formed by light rays which appear to diverge from a point. A virtual image cannot be projected onto a screen.

Question 22

What is focal length?

Answer 22

The distance from the centre of the lens to the focal point is the focal length.