Physics - Waves 1

Transverse waves

The particles vibrate at a right angle to the direction the wave travels in. E.g. light waves, water surface waves

Longitudinal waves

The particles vibrate to and fro in the same direction the wave travels. The wave contains compressions, where particles move together, and refractions, where particles move apart. e.g. sound waves

Oscillation

A vibration i.e a movement back and forth about a fixed point (the rest or equilibrium position)

Displacement

Distance with direction. Measure in metres

Amplitude

The maximum displacement from the rest position of the oscillation. Measure in metres. Symbol a

Time Period

The time taken for one complete cycle. This is when it has reached the same displacement AND is going in the same direction as it was 1 cycle ago. Measured in seconds. Symbol T

Freuqency

How fast an object is vibrating (how many cycles are completed each second). Measure in Hertz (1Hz). Symbol f

Wavelength

The distance between one point on one wave and the same point on the next wave. Measure in metres. Symbol is λ (lambda)

What do waves transfer?

They transfer energy and information without transferring matter

Equation for speed, frequency and wavelength

speed = frequency x wavelength

Equation for frequency and time period

frequency = 1 / time period

Can all waves be reflected?

Yes

What is the electromagnetic spectrum in order?

Radio, microwave, infrared, visible light, ultraviolet, x-ray, gamma ray

What do all the waves in the electromagnetic spectrum have in common?

They all travel at the same speed in free space.

What are some difference in the waves in the electromagnetic spectrum?

They have different wavelengths and frequencies

What is the pattern in wavelengths and frequencies in the electromagnetic spectrum?

From radio → gamma ray: wavelength decreases and frequency increase. Smaller wavelength = higher frequency

Use of radio waves

Broadcasting and communications

Use of microwaves

Cooking and satellite transmissions

Use of infrared

Heaters and night vision equipment

Use of visible light

Optical fibres and photography

Use of ultraviolet

Fluorescent lamps

Use of x-rays

Observing the internal structure of objects and materials, including for medical applications

Use of gamma rays

Sterilising food and medical equipment

Detrimental effect of excessive exposure of microwaves

Internal heating of body tissue

Detrimental effect of excessive exposure of infrared

Skin burns

Detrimental effect of excessive exposure of ultraviolet

Damage to surface cells and blindness

Detrimental effect of excessive exposure of gamma rays

Cancer and mutation

Properties of Light Rays

Light rays are transverse waves and they can be reflected

Law of reflection

The angle of incidence = the angle of reflection