Light And Sound

Question 1

Are light waves transverse or longitudinal ?

Answer 1

Transverse

Question 2

What is reflection ?

Answer 2

Reflection is the process by which a ray of light strikes a Boundary and returns towards that source

Question 3

What is refraction ?

Answer 3

Refraction is the bending of light as it travels from one medium to another. This bending occurs because the speed of the wave changes in different media

Question 4

What is the diffraction ?

Answer 4

When light waves meet a gap in a barrier, they carry on through the gap. However the waves spread out to some extent into the area beyond the gap

Question 5

What is the law of reflection ?

Answer 5

Angle of incidence equals angle of reflection

Question 6

How do you draw rays of light ?

Answer 6

• they are straight lines

* they have arrows that indicate their direction

Question 7

What is the normal ?

Answer 7

And imaginary line at a right angle to the Boundary

Question 8

Where are angles always measured between ?

Answer 8

Ray and the normal, never between the ray and the boundary

Question 9

What is the refractive index ?

Answer 9

How bendy the material is for light, as it tells you how much the speed of light changes through a material

Question 10

What can the refractive index never be below ?

Answer 10

1

Question 11

What is the equation for refractive index ?

Answer 11

Sin(angle of incidence)
Refractive index = ————–
Sin(angle of refraction)

Question 12

What happens to light when it enters a material with a high refractive index ?

Answer 12

Light bends towards the normal

Question 13

What happens to light when it enters a material with a lower refractive index ?

Answer 13

Light bends away from the normal

Question 14

When does total internal reflection occur ?

Answer 14

This only happens in high to low refractive index, and beyond the critical angle

Question 15

Equation for critical angle

Answer 15

1
Sin(C) = —-
n

Question 16

Uses for total internal reflection

Answer 16

Optical fibres and can carry a enormous amount of information as pulses of light

Question 17

Are soundwaves are longitudinal or transverse ?

Answer 17

Longitudinal

Question 18

Can sound travel in a vacuum ?

Answer 18

No

Question 19

How fast does sound travel in air ?

Answer 19

340m/s

Question 20

What is the range of Hz that human can hear ?

Answer 20

20 to 20,000 Hz

Question 21

What is on the X axis of oscilloscope ?

Answer 21

Time per division

Question 22

What is on the Y axis on an oscilloscope ?

Answer 22

Voltage per division

Question 23

How do you find frequency from an oscilloscope ?

Answer 23

• fine two points on the whole wave that are the same
• Measure the distance between them in divisions
• multiply the number of divisions by the timebase setting (X s/div) to get the period of the whole wave (T)
• F = 1/T

Question 24

How do you find amplitude from an oscilloscope ?

Answer 24

• find the tallest point of the wave
• Measure the number of divisions above the centreline of this point
• multiply the number of divisions by the voltage setting (X v/div)

Question 25

Describe analogue

Answer 25

Amplitude and/or frequency constantly vary

Question 26

Describe digital

Answer 26

Consists of pulses with two states on-off.

Question 27

What are the advantages of using digital rather than analogue ?

Answer 27

• Digital signals can carry more information as they have bigger bandwidth and multiplexing
• analogue signals my crackle lose signal as when analogue signals are amplified so can random signals picked up by waves