2.4 Optics

Question 1

What is light?

Answer 1

Electromagnetic radiation visible to the human eye.

Question 2

What do electromagnetic waves consist of?

Answer 2

A magnetic field and electric field travelling together displaced at 90 degrees together.

Question 3

What is the pattern called that electromagnetic waves take?

Answer 3

Sinusoidal.

Question 4

How do colours appear differently to the human eye?

Answer 4

Depending on the frequency or wavelength.

Question 5

If the frequency of the light gets higher what will happen to the colour?

Answer 5

It will appear bluer and bluer until it becomes ultra violet which is the limit of the human eye.

Question 6

If the frequency of the light gets lower what will happen to the colour?

Answer 6

It will appear redder and redder until it becomes infra-red and cannot be detected by the human eye.

Question 7

How are light waves measured?

Answer 7

In Nanometres and Angstroms.

Question 8

What range of wavelengths are visible to the human eye?

Answer 8

Greater than 7000Å (700nm) and less than 4000Å (400nm)

Question 9

What is the speed of light in a vacuum?

Answer 9

186,000 miles per second.

Question 10

What will change the speed of light?

Answer 10

The medium through which the light travels e.g. water makes it slower.

Question 11

What is the formula for speed of light?

Answer 11

Wave x Frequency

Question 12

What are the laws of reflection?

Answer 12

Angle of incidence is equal to angle of reflection
Incident ray, reflected ray and the normal all lie in the same plane.

Question 13

What does the word plane refer too?

Answer 13

A two dimensional space such as a flat mirror.

Question 14

What is the difference between a real and virtual image?

Answer 14

Real- can be projected onto screen, light waves come from an actual object
Virtual- Image appears to come from behind the mirror.

Question 15

What is lateral inversion?

Answer 15

The effect of looking at written text in a mirror.

Question 16

What are the two types of spherical mirror?

Answer 16

Concave and convex.

Question 17

What does a convex mirror do?

Answer 17

De-magnify and provide a wider field of view.

Question 18

What does a convex mirror do?

Answer 18

Magnifies the image.

Question 19

What is refraction?

Answer 19

Change of direction in a wave when it enters another medium.

Question 20

What is the refractive index?

Answer 20

Speed of light in a vacuum divided by the speed of light in the medium which will determine the extent of the ‘bending power’.

Question 21

If the light is bent more through refraction, what does it mean?

Answer 21

The speed of light through the medium is lower.

Question 22

What is snells law?

Answer 22

A formula used to describe the relationship between the angles of incidence and refraction, which gives you the refractive index.

Question 23

What is convex lens also referred too as?

Answer 23

A converging lens

Question 24

What does a convex lens do?

Answer 24

Used to magnify and project, the eye has a convex lens.

Question 25

Convex Lens- What happens when an object is closer to the lens than the focal point?

Answer 25

The image is real, inverted and magnified. It produces an inverted image which is then corrected by the brain.

Question 26

Convex Lens- What happens when an object is beyond the focal point?

Answer 26

The image is virtual, upright and magnified.

Question 27

What is a concave lens referred to as?

Answer 27

A diverging lens.

Question 28

What happens with a diverging lens?

Answer 28

The parallel rays are spread out so they appear to come from the focal point. The image is upright, virtual and diminished.

Question 29

What are some of the advantages of fibre optics over metal wires?

Answer 29

Smaller and lighter
Carry more information (64,000 phone calls simultaneously)
Safer due to no electricity

Question 30

What are some of the disadvantages of fibre optics?

Answer 30

Difficult to terminate
Difficult to repair

Question 31

How is a fibre optic constructed?

Answer 31

High refractive core, low refractive cladding. This gives total internal reflection.

Question 32

Where is the greatest loss of signal in fibre optic?

Answer 32

Connectors and couplings.

Question 33

What is the speed of light?

Answer 33

3.8x10⁸ m/s