2.4 Optics

Question 1

What colour the higher the frequency

Answer 1

Bluer ther light becomes until it turns Ultra Violet

Question 2

What sort of wave is Light

Answer 2

electromagnetic

Question 3

What colour the lower the frequency

Answer 3

The redder it will appear until its turn Infra Red

Question 4

Light waves have very small wavelengths and they are measured in Nanometres and Angstroms. What are thier values?

Answer 4

1 Nanometre (nm) = 1 × 10−9 m

1 Angstrom (Å) = 1 × 10−10 m or 0.1 nm

Question 5

Wavelengths greater than or 700 nm and less than or 400 nm will be

Answer 5

Invisible to the eye

Question 6

Speed of Light in a vacuum

Answer 6

186 000 miles per second
or
300,000,000 metres per sec (3 x 10^8 m/s)

Question 7

Speed of Light through water

Answer 7

224 000 kilometre per sec

Question 8

Speed of Light through Glass

Answer 8

200 000 kilometre per sec

Question 9

Speed of Light through Diamond

Answer 9

124 000 kilometre per sec

Question 10

Formula for speed of light

Answer 10

speed of light = wavelength x freq

Question 11

In a flat mirror, the angle of incidence =

Answer 11

The angle of reflection

Question 12

The image created by a mirror or lens can be

Answer 12

real or virtual

Question 13

For plane mirrors, the image formed is:

Answer 13

• the same size as the object
• as far behind the mirror as the object is in front
• virtual
• laterally inverted or back to front but the right way up.

Question 14

There are two types of spherical mirrors:

Answer 14

concave and convex.

Question 15

Define a convex mirror?

Answer 15

curves outward, toward the light source. The reflected rays from a convex mirror diverge, making the image appear smaller and providing a wider field of view.

Question 16

Define a concave mirror?

Answer 16

curves inwards, away from the light source. If the object is close to the mirror, a magnified, upright and virtual image is formed, whereas if the object is far from the mirror, a diminished, inverted and real image is formed. Concave mirrors may be found in make-up kits and dentists tools, to provide a magnified view.

Question 17

What is refraction

Answer 17

The change in direction of a wave when it enters a different medium i.e Water, However, when the light ray is perpendicular to the surface it changes speed but not direction.

Question 18

What is refractive index? And the formula…?

Answer 18

The refractive index of a material is the ratio of the speed of light in a vacuum compared to the speed of light in the material. The bigger the refractive index the more light will bend when entering and leaving the material.

n = c / v
* n = refractive index
* c = speed of light in a vacuum
* v = Speed of light in the material (m/s)

Question 19

What is Snell’s law used for?

Answer 19

Its a formula used to describe the relationship between the angles of incidence and refraction. From this relationship it is possible to determine the refractive index of a material by looking at the angle of refraction.

Question 20

How do lenses work for images?

Answer 20

Lenses form images in much the same way as curved mirrors but by refraction rather than reflection.

Question 21

Define a convex lens?

Answer 21

Also referred to as a converging lens, its thicker at its centre than at the edges. A convex lens may form either a real or virtual image depending on the positions of the object and the observer.

Question 22

Define a Concave Lens?

Answer 22

A concave lens, also referred to as a diverging lens, is thinner at its centre. The image formed by a concave lens is always upright, virtual, and diminished.

Question 23

What are Fibre optics made from

Answer 23

A fibre is a hair-thin strand of glass or plastic

Question 24

Fibre optics have certain advantages over metal wires, what are they?

Answer 24

• Lighter and Smaller
• Able to carry more info
• Instrinsically safer

Question 25

Disadvantage of Fibre Optics

Answer 25

Difficult to terminate

Question 26

What does a fibre optic core have?

Answer 26

High refractive index

Question 27

What does the cladding of a fibre have?

Answer 27

A low refractive index