Electromagnetic waves up to level 6

Question 1

What are all of the electromagnetic waves in order of their wavelength (longest to shortest)?

Answer 1

Radio waves

Microwaves

Infra red

Visible light

Ultraviolet

X-ray

Gamma

Question 2

What are the electromagnetic waves in order of frequency (higest to lowest)?

Answer 2

Gamma rays

X-rays

Ultraviolet

Visible light

Infra red

Microwaves

Radio waves

Question 3

What is the relationship between the frequency of an electromagnetic wave and its energy

Answer 3

The higher the frequency of the wave, the higher the enrgy it has

Question 4

Compare the speeds of the different types of electromagnetic waves in a vacuum

Answer 4

All electromagnetic waves travel at the same speed in a vacuum.

The speed that they travel at is 300,000,000 m/s (3x10⁸ m/s)

Question 5

What is the range of wavelengths that can be detected by the human eye

Answer 5

400 nm (violet light) to 750 nm (red light)

Question 6

Explain what white light is made of

Answer 6

White light is made of a range of colours. These colours are:

Red, Orange, Yellow, Green, Blue, Indigo, Violet

When these colors are all added together the result is white light.

Question 7

Give two uses of visible light and explain why it is useful for this purpose

Answer 7

Visible light is used for sight. This isuseful for this purpose becuase it can penetrate through the atmosphere down to the surface of the earth.

It is also used for fibre optics. It is useful for this becuase it has a high frequency, so it can carry a lot of informaiton, but is not ionising.

Question 8

Give two uses of microwaves and explain why they are suitable for this role.

Answer 8

Microwaves can be used for cooking. This is becuase they can penetrate through food and are absorbed by water, which gives energy to the water molecules and causes them to heat up

They are also used in mobile phone communicaitons. This is becuase it is non-ionising and can penetrate quite far through the atmosphere, but not far enough to interfere with other mobile phone systems

Question 9

Give two uses of radio waves and explain why they are used for this role

Answer 9

They are used to send TV and radio signals. This is becuase they are non ionising, can penetrate walls and buildings and will diffract around large obstacles such as mountains.

They are also used for blutooth communicaiton as they are low energy to produce (compared to other types of wave) and are non-ionising.

Question 10

Explain how to show that the low of reflection occurs with microwave signals

Answer 10

1. Set up the equipment as shown in the diagram
2. Draw a normal on a piece of paper below the metal plate. A normal is a line which is at 90˚ to the surface
3. point the transmitter at the normal from one side, and measure the angle made between the incident ray (the ray hitting the surface) and the normal
4. Move the reciver (but keep it ointing at the normal) until you pick up the microwaves
5. Measure the angle made between the rays exiting the surface (reflected rays) and the normal. If the law of reflection applies these angles should be the same

Question 11

Which two waves are used for sending communications through the atmosphere?

What is the relationship between the frequency of the wave and the rate of data transfer (how fast it can transfer data)?

Answer 11

Microwaves and radio waves are both used for communications through the atmosphere.

The higher the frequcy of the wave, the faster the rate of data transfer. This means that higher frequency waves can send the same amount of data in a shorter time.

Question 12

What are radio waves used for if they have a wavenegth of:

1) less than 1 metre?
2) 1m to 100m?
3) greater than 100m?

Answer 12

1) radio waves of wavelength less than 1 m are used for TV broadcasts. This is becuase they have a higher frequency so can send information more quickly

Wavelengths of 1m to 100m are used for local radio. This is because they have a limited range through the atmosphere (they are absorbed as they travel) so they can only be detected in the area surrounding the mast

Wavelengths of >100m are used for national radio becuase they have a much larger range in air (can travel much further)

Question 13

Explain why optical fibre cables use visible light to carry the information rather than radio waves

Answer 13

Visible light has a much higher frequency than radio waves. This means that it can transfer information at a much faster rate.

Question 14

Explain how a mobile phone network operates.

Answer 14

1. The mobile phone sends a microwave signal to a mast
2. The signal is then sent (usually via cables) to a central exchange (also called sa switching centre)
3. The central exchange then sends the signal to another mast
4. the second mast sends out a microwave signal to the reciving mobile phone

Question 15

Is there a link between mobile phone microwave signals and damage to peoples brains?

Answer 15

At the moment there has been no link found.

More research needs to be carried out though, so at the moment it is recommended that children use them for limited times only becuase they have thinner skulls than adusts, so less protection from the microwaves (as the bone will stop a lot of the wave from travelling through)

Question 16

How do high frequency waves (gamma rays, X-rays and ultraviolet) damage the human body

Answer 16

These rays damage the human body by ionisation.

Ionisation is when the wave knocks an electron off of an atom. This leaves a positive ion becuase it has more protons than electrons.

Question 17

What are the main problems caused by ionising radiation?

Answer 17

If ionising radiation ionises the DNA it can lead to cancer. Cancer is a group of cells that will not stop dividing.

If ionising radiation also ionises the DNA of cells in our skin then it can leat to the apperarance of aged skin

Question 18

What is the main use of ultraviolet (UV) radiaiton?

What is the main danger of UV radiation?

Where does most of our exposure to UV radiaiton come from?

Answer 18

UV radiation is used to get a sun tan, this means it is used in sunbeds and subathers (as it is emitted from the sun)

UV radiation can cause skin cance becuase it can ionise skin cells

Most of our exposure to UV radiation comes from the sun and from sunbeds

Question 19

What is the main use of x-ray radiaiton

What are the main problems of x-ray radiation

Answer 19

The main use of x-ray radiation is for medicine. It is used in X-ray machines to create a picture of the bones. This works becuase the x-rays can pass through soft tissure (skin and muscle) to reache a detector but cannot pass through bone.

X-rays can also be used in x-ray therapy. This is where high doese of x-rays are used to kill cancerous cells in the patients body.

The main problem with using x-ray radiation for medical diagnosis is that it can cause cancer. This occurs becuase it is ionising radiation and can ionise the DNA in our cells.

Question 20

What are the main uses of gamma radiation?

What is the main problem with using gamma radiation?

Answer 20

the main use of gamma radiation is used in medical diagnosis. A radioactive tracer is injected into the body and can then be detected outside of the body. This can be used to diagnose disease.

Gamma radiaiton is also used to sterilise food and medical equipment. This is becuase it can penetrate through the substance, and will ionise the bacteria cells, killing them.

The main problem with using gamma radiation for medical diagnosis is that it can cause cancer. This occurs becuase it is ionising radiation and can ionise the DNA in our cells.

Question 21

Explaiin why X-rays and gamma rays will cause cancer all over the human body, but ultraviolet rays will only cause skin cancer

Answer 21

X-rays and gamma rays can penetrate right the way through the body. This means that they can ionise all the cells in the human body and cause cancer.

Ultraviolet rays are absorbed by skin. This means that they will only cause skin cancer as they cannot travel deeper into the body.

Question 22

Where do X-rays come from?

Where do gamma rays come from?

Answer 22

X-rays are produced by the electrons in an atom. If an electron is in a high energy level it can drop down to a lower energy level. The energy it has lost will be emitted as an X-ray. They are also produced in x-ray tubes when fast moving electrons are suddenly slowed down, relasing energy as an x-ray

Gamma rays are produced in the nucleus of an atom. If the nucleus has too much energy it will release some of that energy as a gamma ray