Topic 5 - Light & The EM Spectrum

Question 1

Reflection

Answer 1

• Wave changes direction back to the same medium at a boundary

Question 2

Refraction

Answer 2

• Wave changes direction when traveling into a different media at a boundary

Question 3

Total Internal Reflection

Answer 3

• Light ray travels from denser to less dense material, and there is no refracted ray as it is on the boundary

Question 4

Critical angle

Answer 4

• The angle of incidence when it causes the refacted ray to bend 90 degrees to the normal, and on the boundary

Question 5

Specular Reflection

Answer 5

• Reflection in a single direction

Question 6

Diffuse Reflection

Answer 6

• Reflection causing scattering

Question 7

How is colour of light related to differential absorption at surfaces?

Answer 7

• Surface absorbs every frequency of light except the colour it is

Question 8

How is colour of light related to transmission of light through filters?

Answer 8

• Filters absorb certain wavelength, and transmit others

Question 9

Relate power to focal length

Answer 9

• Higher the power, the lower the focal length

Question 10

Equation for power:

Answer 10

P=1/Focal length (meters)

Question 11

Description of real images:

Answer 11

• Converging lenses only
  2 rays are drawn:
• 1 through the centre of the lens
• 1 parallel to the axis until it hits the lens, then refracts to the focal point

Question 12

Description of virtual images:

Answer 12

• Both Converging and Diverging
  3 rays are drawn: (Converging)
• 1 through the centre of the lens
• 1 parallel to the axis until it hits the lens, then refracts towards the focal point
• 2 rays go opposite direction until they meet

3 rays are drawn: (Diverging)

• 1 throught the centre of the lens
• 1 parallel to the axis until it hits the lens, then refracts away from the focal point, and one in the opposite direction to that

Question 13

EM waves transfer energy from source to:

Answer 13

observer

Question 14

EM spectrum in order of increasing frequency:

Answer 14

• Radio waves
• Microwaves
• Infrared
• Visible Light
• Ultraviolet
• X-Rays
• Gamma

Question 15

Effects of differences in the velocities of EM waves in different substances

Answer 15

Dispersion, which is:
- Light slowing down through different materials more for some colours more than others

Question 16

All bodies emit:

Answer 16

• Radiation, dependant on temperature

Question 17

For a body to be at a constant temperature, it needs to:

Answer 17

• Radiate the same average power that it absorbs

Question 18

If a body’s average power it radiates is less than the average power it absorbs:

Answer 18

• Its temperature will increase

Question 19

If a body’s average power it radiates is more than the average power it absorbs:

Answer 19

• Its temperature will decrease

Question 20

Factors controlling the temperature of Earth

Answer 20

• Greenhouse effect
• Sun
• Human activities

Question 21

Effects on people due to exposure of EM waves

Answer 21

• Microwaves: internal heating
• Infrared: skin burns
• UV: damage to surface cells. causing cancer and eye conditions
• Gamma: Mutations or damage to cells

Question 22

Uses of EM waves:

Answer 22

Radio waves: Broadcasting and comms
Microwaves: Cooking and comms
Infrared: Thermal imaging, and TV controllers
Visible Light: Vision
UV: Security searching and forged bank notes
X-rays: Observing internal structure
Gamma: Sterilisng foods, detect cancer

Question 23

Radiowaves are produced by:

Answer 23

oscillations in electrical currents

Question 24

Finish the sentence - Changes in atoms and nuclei:

Answer 24

• can generate radiations
• are caused by absorbing a range of radiations