Waves

Question 1

what is a wave?

Answer 1

means of energy transfer through vibration of particles

Question 2

what is vibration?

Answer 2

repeated movement of a body about a fixed point

Question 3

what is a transverse wave?
examples

Answer 3

a wave in which particles vibrate perpendicular to the direction of energy transfer
- light
- microwaves
- infra red
- radio waves
- x-ray
- UV waves

Question 4

what are longitudinal waves?

Answer 4

a wave in which particles vibrate parallel to the direction of energy transfer
- sound waves
- ultra sound

Question 5

what is compression?

Answer 5

a region in a longitudinal wave where particles are closely packed together leading to a high pressure zone and high density

Question 6

what is rarefaction?

Answer 6

a region in a longitudinal wave where particles particles are far apart leading to a low pressure zone and low density

Question 7

what is displacement, x?

Answer 7

perpendicular distance moved by a particle in a wave from its mean position

Question 8

what is amplitude ,A?

Answer 8

maximum displacement and the loudness of a sound wave

Question 9

what is wave length (lamda) ?

Answer 9

distance between 2 consecutive crests/troughs

Question 10

what is a period, T ?

Answer 10

time taken for a complete oscillation

Question 11

what is frequency, f ?

Answer 11

number of cycles per unit time
= n.o. of cycles/ time
Hertz , Hz

Question 12

wave equation

Answer 12

speed = distance / time
= wavelength / time
speed of wave is 2cm per second

Question 13

reflection of waves

Answer 13

the bouncing back of a wave from a boundary or surface

Question 14

what is diffraction?

Answer 14

the spreading of a wave as it passes past an obstacle or gap

Question 15

applications of diffraction?

Answer 15

wifi
spreading of signals in hilly areas
radar and sonar usage

Question 16

what is refraction?

Answer 16

the change in direction and speed of a wave as it passes from one medium to another

Question 17

what are sound waves?

Answer 17

a form of longitudinal waves that consist of compressions and rarefactions

Question 18

speed of sound waves

Answer 18

solids - 5000 m/s
liquids - 1500 m/s
gases - 330 - 340 m/s

Question 19

use of a CRO

Answer 19

used to determine a period, frequency, amplitude of a wave

Question 20

what is light?

Answer 20

consists of photons which contain energy of frequency in the range of visible light

Question 21

properties of light

Answer 21

• transverse wave
• can travel through a vacuum
• travels at 3.0 x 10^8 m/s
• can be polarized
• travels in straight line

Question 22

laws of reflection

Answer 22

1. at a point of incidence, angle of incidence = angle of reflection
2. normal, incident, and reflected ray lie in the same plane

Question 23

what is a virtual image?

Answer 23

an image that cannot be cast on a screen and formed by extensions of reflected or refracted rays

Question 24

what is refraction?

Answer 24

angle of incidence in a dense medium which causes refracted rays to graze the boundary
n = sin90 / sin c

Question 25

what is refractive index, n?

Answer 25

ratio of the speed of light in air to the speed of light in a medium
n = sin i / sin r ALSO v = lamda x f

Question 26

total internal reflection

Answer 26

occurs in a denser medium when the angle of incidence is greater than critical angle i>c

Question 27

challenges of using a ray box

Answer 27

the beam is not parrallel so it spreads out

Question 28

applications of total internal reflection

Answer 28

used in optical fibres for:
1. transmission of internet signal
2. endoscopy in endoscopes for non-invasive medical diagnosis

Question 29

types of lenses

Answer 29

converging lens - convex
diverging lens - concave

Question 30

what is principal focus?

Answer 30

point on the principal axis where all rays parallel and close pass after being refracted

Question 31

what is focal length?

Answer 31

length between the principal focus and the center

Question 32

real image

Answer 32

image formed by actual intersection of refracted or reflected rays

Question 33

what is a convex lens?

Answer 33

a lens that converges rays of light that convey parallel to its principal axis

Question 34

what is a concave lens?

Answer 34

shaped round inwards at the centre and bulges outwards through the edges, making the light diverge

Question 35

difference between a convex and concave lens?

Answer 35

A concave lens is thicker at the edges and thinner at the centre. A convex lens is thicker at the centre and thinner at the edges