Waves

Question 1

Wave motion

Answer 1

Transfer of energy from one place to another

Question 2

Frequency (f)

Answer 2

Number of cycle or waves in one second, unit hertz (Hz)

Question 3

Wavelength (λ)

Answer 3

Length of one complete wave, unit, meters (m)

Question 4

Amplitude (a)

Answer 4

Maximum displacement of medium from its mean position, meters

Question 5

Wavefront

Answer 5

Line where the disturbance of all particles are at the same point from the central position
eg. a crest of a wave is a wavefront

Question 6

Wave equation (x2)

Answer 6

v = f x λ

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

f = 1 / T
T is the time period of the wave in seconds

Question 7

Movement of particles (in 2 different waves)

Answer 7

Longitudinal waves=> back and forth parallel to the direction of the waves (oscillate along the same direction as the energy transfer/ direction of wave)

Transverse waves=> perpendicular to the direction of the waves (up and down)

Question 8

Law of reflection

Answer 8

Angle of incidence (i) = angle of reflection

angle iº = angle rº

Question 9

Refraction in relation to mediums and normal line

Answer 9

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

Question 10

Refractive index (n)

Answer 10

n = sin iº in air or vacuum / sin rº in material

n = speed of light in air or vacuum / speed of light in material

Question 11

Diffraction

Answer 11

Bending of waves around the edges of a hard surface

Question 12

Dispersion

Answer 12

Separation of different waves according to colours or frequency for example by using a prism

Question 13

Image from a plane mirrors

Answer 13

Virtual, upright, same size and laterally inverted and same distance from the mirror inside

Question 14

Image from a convex lens

Answer 14

When close: virtual, enlarge, upright
When far: real, small, upside down

think about it like a magnifying glass

Question 15

Image from a concave lens

Answer 15

Virtual, upright, small

Question 16

Critical angle

Answer 16

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

Question 17

Total internal reflection (TIR)

Answer 17

When light goes from denser to lighter medium, the refracted ray bend inside the same medium called (TIR) eg optical fibre

Question 18

Electromagnetic Spectrum: travel in vacuum, oscillating electric and magnetic fields
←λ (decrease) and f (increase)
λ (increases) and f (decrease)→

Answer 18

←λ (decrease) and f (increase)
λ (increases) and f (decrease)→

Gammas rays
X-Rays 
Ultra violet rays
Visible (light) rays
Infrared rays
Micro waves
Radio waves

Question 19

Rays and their uses

Answer 19

Gamma rays: for killing cancer cells
X-rays: in medicine
UV rays: for sun tan and sterilisation of medical instruments
Visible light: light rays, monochromatic means one colour
Infrared: remote controls, treatment of muscular pain
Micro waves: international communication, mobile phones
Radio waves: radio and television communication

Question 20

Colours of visible light VIBGYOR wavelengths

Answer 20

Violet 4×10^-7m, Indigo, Blue, Green, Yellow, Orange, Red 7×10^-7m

Question 21

Speed of light waves or electromagnetic waves

Answer 21

In air:
3×10^8 m/s

In water:
2.25×10^8 m/s

In glass:
2×10^8 m/s

Question 22

Light wave

Answer 22

Transverse electromagnetic waves

Question 23

Sound wave are longitudinal waves

Answer 23

particles of the medium come close to each other → compression
particles of the medium move away → rarefaction

Question 24

Echo

Answer 24

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 25

Properties of sound waves in relation to the shape of the wave

Answer 25

Pitch is similar to the frequency of the wave

Loudness is similar to the amplitude of the wave

Question 26

Speed of sound waves

Answer 26

Air:
330-340 m/s

Water:
1400 m/s

Concrete:
5000 m/s

Steel:
6000–7000 m/s

Question 27

Diffraction rules

Answer 27

Greater frequency means greater diffraction and more wave cycles

Greater gap less diffraction

Greater wavelength greater diffraction