light and lasers

Question 1

give an example of digital signal?

Answer 1

signalling lamps

Question 2

what questions do we have to ask about the method of transmission? advantages and disadvantages

Answer 2

can the signal be seen by others?
can wires be cut?
how far does the signal have to travel?

Question 3

how is laser light used to read from the surface of a compact disc?

Answer 3

• the surface of the CD is pitted
• the pits represent the digital signal
• laser light is shone onto the CD surface and the difference in the reflection provides the information for the digital signal.

Question 4

what happens when light travels from one material to another?

Answer 4

it is normally refracted

Question 5

what happens if a light is passed from a more dense material into a less dense?

Answer 5

the angle of refraction is larger than the angle of incidence

Question 6

complete this sentence… when the angle of refraction is 90 degrees, the angle of incidence is called the…

Answer 6

critical angle

Question 7

what happens if the angle of incidence is bigger than the critical angle?

Answer 7

the light is reflected; this is can be called total internal reflection

Question 8

at what speed are telephones data transmitted along optical fibres

Answer 8

(200 000 km/s in glass)

Question 9

what piece of equipment is used to allow doctor to see into a body without surgery

Answer 9

an endoscope

Question 10

explain how an endoscope works

Answer 10

light passes along one set of optical fibres to illuminate the inside of the body. The light is reflected. The reflected light passes up another set of fibres to an eyepiece or camera.

Question 11

what does a laser produce?

Answer 11

a narrow intense beam of light of a single colour

Question 12

what is a laser capable of doing?

Answer 12

cutting, burning or vaporising materials

Question 13

name 3 uses of lasers?

Answer 13

surgery, communication, bar code readings

Question 14

how can signals be sent?

Answer 14

by light, electricity, radio waves or microwaves

Question 15

what are advantages of signals?

Answer 15

they are almost instantaneous

Question 16

what is an adv and a dis about light signals?

Answer 16

they can be easily sent with little equipment. However the signal needs to be coded and is not secure. Anyone can see what is being sent

Question 17

what is an adv and a dis about electrical signals?

Answer 17

they need equipment and wires linking the sender and receiver of the signal. Wires could be cut or damaged.

Question 18

what is an adv and a dis about radio waves and microwaves?

Answer 18

they can travel large distances and through the atmosphere. They can even travel across space

Question 19

what does coherant mean? (2 points)

Answer 19

the same frequency

in phase with each other.