Waves, light and sound

Question 1

Wave equation 1

Answer 1

v = f x λ

v is the speed of wave in m/s
f is the frequency in Hz
λ is the wavelength in meters

Question 2

Wave equation 2

Answer 2

f = 1 / T

T is the time period of wave in
seconds

Question 3

Movement of the particles

of the medium

Answer 3

Longitudinal waves=> back and forth in the direction of the
waves
Transverse waves=> perpendicular to the direction of the waves

Question 4

Law of reflection

Answer 4

Angle of incidence i = angle of reflection

                     angle i = angle r

Question 5

Refraction

Answer 5

From lighter to denser medium → light bend towards the normal
From denser to lighter medium →light bend away from the
normal

Question 6

Refractive index n

Answer 6

n = sin∠ i / sin∠r

*Refractive index has no unit

Question 7

Refractive index n

Answer 7

n = speed of light in air or vacuum / speed of light in any other medium

Question 8

Image from a plane mirror

Answer 8

Virtual, upright, same size and laterally inverted,

same distance from the mirror inside

Question 9

Image from a convex lens

Answer 9

When close: virtual, enlarge, upright

When far: real, small, upside down

Question 10

Image from a concave lens

Answer 10

Virtual, upright, small

Question 10

Image from a concave lens

Answer 10

Virtual, upright, small

Question 11

Critical angle

Answer 11

When light goes from denser to lighter medium, the incident
angle at which the reflected angle is 90 o
,is called critical angle

Question 12

Total internal

reflection (TIR)

Answer 12

When light goes from denser to lighter medium, the refracted ray
bend inside the same medium then this is called (TIR)

Question 13

Electromagnetic spectrum

Answer 13

In order of increasing frequency:
Radio waves
Micro waves
Infra red
Visible light
Ultraviolet
 X-rays 
Gamma rays

Question 14

Colours of visible

spectrum (light)

Answer 14

R- red
O- orange
Y- yellow
G- green
B- blue
I- indigo
V- violet

Question 15

Speed of light

Answer 15

In air : 3 x 10 ^8 m/s

In light : 2 x 10 ^8 m/s

Question 16

Light wave

Answer 16

Electromagnetic wave

Question 17

Sound wave

Answer 17

Longitudinal waves
particle of the medium come close → compression
particles of the medium far apart → rarefaction

Question 18

Echo

Answer 18

v = 2 x d /t

v is the speed of sound waves,
d is the distance in meters between source and the reflection surface,
t is the time for echo

Question 19

Properties of sound waves

Answer 19

Pitch means the frequency of the wave

Loudness means the amplitude of the wave

Question 20

Speed of sound waves

Answer 20

Air : 330-340 m/s
Water: 1400 m/s
Concrete : 5000 m/s
Steel: 6000 – 7000 m/s