Properties of waves and the EM spectrum

Question 1

What is light part of?

Answer 1

A continuous spectrum that all travels at the same speed in free space

Question 2

What is the order of the EM spectrum from low frequency to high frequency?

Answer 2

Radio waves, microwaves, infrared radiation, visible light, ultraviolet, X-rays, gamma rays

Question 3

What is the order and wavelengths from lowest frequency to highest frequency of the colours in visible light?

Answer 3

Red 700nm, Orange 650nm, Yellow 570nm, Green 510nm, Blue 475nm, Indigo 445nm and Purple 400nm

Question 4

What are the uses, risks and preventions of radio waves?

Answer 4

• Broadcasting and communication
• Long exposure can cause damage
• N/A

Question 5

What are the uses, risk and preventions of microwaves?

Answer 5

• Cooking and satellite transmissions
• Skin burns, cataracts and internal heating of tissue
• Microwaves have metal screens that reflect waves to keep them in

Question 6

What are the uses, risks and preventions of infrared radiation?

Answer 6

• Heaters and night vision equipment
• Burns and loss of vision due to long exposure
• Reduce exposure

Question 7

What are the uses, risks and preventions of ultraviolet?

Answer 7

• Fluorescent lamps
• Damage and mutation of cells and cell death
• Reduce exposure, protective googles/glasses and sun cream

Question 8

What are the uses, risks and preventions of X-rays?

Answer 8

• Observing the internal structure of objects and materials, for medical reasons
• Increased cancer risk and general damage to cells
• Reduce exposure

Question 9

What are the uses, risks and preventions of gamma rays?

Answer 9

• Sterilising food and medical equipment
• Cell damage, cancer and cell mutation
• Lead to reduce exposure

Question 10

All waves can be reflected and…

Answer 10

Refracted

Question 11

Φi

Answer 11

Φr

Question 12

Sin(i)

Answer 12

n*sin(r)

Question 13

How do you measure the refractive index of a glass block?

Answer 13

1. Shine a ray of light onto one side of the glass block so that the ray emerges on the opposite side. Mark the direction of both of these rays
2. Draw around the glass block before removing it
3. Draw the ray that travelled inside the block
4. Draw a normal line
5. Measure the angles of incidence and refraction
6. Use the Snell’s law to work out the refractive index of the glass block

Question 14

How does a speed gun work?

Answer 14

• The Doppler effect
• Reflection causes a Doppler shift
• Squished causing a shorter wavelength and higher frequency
• Wave speed remains the same