Unit 1: Chapter 6 - Electromagnetic Waves

Question 1

The Electromagnetic Spectrum

Wave speed equation?

Order of Electromagnetic Spectrum?

Answer 1

ELECTROMAGNETIC SPECTRUM

Radio (Km wavelength) - low energy, long wavelength
Microwave
Infrared (mm wavelength)
Light
Ultraviolet (Nanometre)
X-ray
Gamma (Pico metre) - High energy, high frequency

Wave speed = Frequency X Wavelength

Question 2

Light, Infrared, Microwaves and Radio Waves

Light uses?

Infrared uses?

Micro waves VS. Radio waves?

Radio waves uses?

Answer 2

LIGHT AND COLOUR
Light is seen as white light. It can be split up a prism to see the colours of the white light as a rainbow.
- Film Camera
- Digital Camera

INFRARED
The hotter an object, the more infrared it emits.
Infrared can be absorbed by the skin and kill cells.
- Optical fibres
- Remote Control Handsets
- Infrared scanners
- Infrared cameras

MICROWAVES
Microwaves lie between radio and infrared waves. They are shorter in wavelength than radio waves. Microwaves can be used for communication e.g. Satellites TV because they can pass through the atmosphere. Microwaves don’t spread out as much as radio waves. They can also be used to carry MOBILE SIGNALS.

RADIO WAVES
300,000 HZ - 3000 million H
We use radio waves for:
- Radio
- TV
- Mobile phone signals

We can use radio waves instead of cables to connect to advices. For example, Bluetooth which has frequencies of 240 million Hz use wireless connections.

Question 3

Communications

Large wavelength VS. Short Wavelength?

Radio waves communication uses?

Micro wave communication uses?

Optical fibres VS. Radio and micro waves?

Answer 3

The radio waves and microwaves are divided into BANDS of different wavelengths because the shorter the wavelength:

• the more information they can carry
• the shorter their range (due to absorption of atmosphere)
• the less they spread out (because they diffract less)

RADIO WAVELENGTHS

Approximately 1M - TV broadcasting from TV masts because they can carry more information than longer radio waves.

1M - 100M - Local Radio stations and Emergency Services because the range is limited to the area around the transmitter.

Greater than 100M - National and International radio stations because they have longer ranges than shorter radio waves.

MICROWAVES

They are used for satellite phones and TV links and satellite TV broadcasting. This is because microwaves can travel between satellites in space to the ground. They spread out much less than radio waves so the signal does;t weaken much.

Although mobile phones utilise radio waves that are very short, they are often referred to as microwaves as they have similar heating effects.

OPTICAL FIBRES

They use light and infrared to transmit signals in very thin glass fibres. The light rays are reflected inside the glass and cannot escape.

In comparison to radio waves:

• Optical Fibres carry much more information - smaller wavelength and carries more pulses of waves.
• More secure as the signals stay within the fibres.

Question 4

Expanding Universe

What is the Doppler effect?
Where can it be observed?

What is Red-Shift?

What is Blue-Shift

What is the relationship between the size of the shift and the speed of the galaxy?

Answer 4

The Doppler effect is the change in wavelength (and frequency) due to motion of the source of waves. This can be observed by an ambulance’s siren as it moves past you.

Another example can be observed in space:

We can tell if a galaxy is moving away from us or towards us with the SPECTRUM OF LIGHT (Blue to Red):

• The light waves are stretched out if the star or galaxy is moving away from us. The wavelength INCREASES. We call this RED-SHIFT because the spectrum of light is shifted towards the red part of the spectrum.
• If the light waves are squashed, this means the galaxy or star is moving towards us. The wavelength is REDUCED. We call this BLUE-SHIFT because the spectrum of light is shifted towards the blue part of the spectrum.

The bigger the shift the more the waves are squashed or stretched. So the faster the galaxy or star is moving towards or away from us.

THE FASTER A STAR OR GALAXY IS MOVING (RELATIVE TO US), THE BIGGER THE SHIFT IS.

All galaxies are moving away from each other so that means the whole universe is expanding.

Question 5

The Big Bang

Answer 5

There was 2 theories to