waves

Question 1

Front

Answer 1

Back

Question 2

What is a wave?

Answer 2

A disturbance that transfers energy without transferring matter.

Question 3

Define transverse wave.

Answer 3

A wave where oscillations are perpendicular to the direction of energy transfer.

Question 4

Define longitudinal wave.

Answer 4

A wave where oscillations are parallel to the direction of energy transfer.

Question 5

Give an example of a transverse wave.

Answer 5

Light waves or waves on a string.

Question 6

Give an example of a longitudinal wave.

Answer 6

Sound waves in air.

Question 7

Define wavelength (λ).

Answer 7

The distance between two consecutive points in phase (e.g. crest to crest).

Question 8

Define frequency (f).

Answer 8

The number of wave cycles passing a point per second (Hz).

Question 9

Define period (T).

Answer 9

The time for one complete wave cycle; T = 1/f.

Question 10

Define wave speed (v).

Answer 10

The distance a wave travels per unit time; v = fλ.

Question 11

What is amplitude (A)?

Answer 11

The maximum displacement of a point from its equilibrium position.

Question 12

Write the wave equation.

Answer 12

v = fλ.

Question 13

How is wave speed affected by the medium?

Answer 13

It depends on the medium’s properties (density and elasticity).

Question 14

What is phase difference?

Answer 14

The difference in phase angle between two points on a wave.

Question 15

Formula for phase difference between two points separated by distance x?

Answer 15

φ = (2πx)/λ.

Question 16

Define angular frequency (ω).

Answer 16

ω = 2πf.

Question 17

Define wave number (k).

Answer 17

k = 2π/λ.

Question 18

Equation of a travelling wave moving in +x direction.

Answer 18

y = A sin(ωt - kx).

Question 19

What does “in phase” mean?

Answer 19

Two points oscillate together, with zero phase difference.

Question 20

What does “antiphase” mean?

Answer 20

Two points oscillate 180° (π radians) out of phase.

Question 21

SI unit of frequency?

Answer 21

Hertz (Hz).

Question 22

State the law of reflection.

Answer 22

Angle of incidence = angle of reflection.

Question 23

What happens to frequency during reflection?

Answer 23

Frequency remains unchanged.

Question 24

What is refraction?

Answer 24

Change in direction of a wave as it passes between media of different densities.

Question 25

What causes refraction?

Answer 25

Change in wave speed when entering a different medium.

Question 26

What happens to wavelength during refraction?

Answer 26

Wavelength changes; frequency stays constant.

Question 27

Write Snell’s law.

Answer 27

n₁ sinθ₁ = n₂ sinθ₂.

Question 28

Define refractive index (n).

Answer 28

n = c/v, where c = speed of light in vacuum.

Question 29

What is total internal reflection (TIR)?

Answer 29

When light reflects entirely within a medium rather than refracting out.

Question 30

Conditions for TIR?

Answer 30

Light travels from denser to rarer medium, incidence angle > critical angle.

Question 31

Define critical angle.

Answer 31

The angle of incidence for which refraction is 90°.

Question 32

What is diffraction?

Answer 32

The spreading of waves as they pass through a gap or around an obstacle.

Question 33

When is diffraction most noticeable?

Answer 33

When the gap size is similar to the wavelength.

Question 34

Define the principle of superposition.

Answer 34

Resultant displacement is the sum of individual displacements.

Question 35

Define constructive interference.

Answer 35

When waves meet in phase, producing larger amplitude.

Question 36

Define destructive interference.

Answer 36

When waves meet in antiphase, producing reduced or zero amplitude.

Question 37

What is a coherent source?

Answer 37

Sources with constant phase difference and same frequency.

Question 38

Path difference for constructive interference?

Answer 38

nλ (n is integer).

Question 39

Path difference for destructive interference?

Answer 39

(n + ½)λ.

Question 40

Experiment demonstrating interference in light?

Answer 40

Young’s double-slit experiment.

Question 41

Fringe spacing formula in Young’s double slit?

Answer 41

w = λD/s.

Question 42

What happens to fringe spacing when wavelength increases?

Answer 42

Fringe spacing increases.

Question 43

What happens to fringe spacing when slit separation increases?

Answer 43

Fringe spacing decreases.

Question 44

What happens to fringe spacing when screen distance increases?

Answer 44

Fringe spacing increases.

Question 45

What is a stationary wave?

Answer 45

Formed by superposition of two equal waves travelling in opposite directions.

Question 46

What are nodes?

Answer 46

Points of zero amplitude.

Question 47

What are antinodes?

Answer 47

Points of maximum amplitude.

Question 48

Distance between adjacent nodes?

Answer 48

λ/2.

Question 49

Define fundamental frequency.

Answer 49

The lowest frequency at which a system can resonate.

Question 50

Frequency of nth harmonic for a string?

Answer 50

fₙ = n(v/2L).

Question 51

How does tension affect string frequency?

Answer 51

Higher tension increases wave speed and frequency.

Question 52

Effect of mass per unit length on frequency?

Answer 52

Greater mass per length decreases frequency.

Question 53

First harmonic in open pipe?

Answer 53

Two antinodes at ends, one node in centre.

Question 54

First harmonic in closed pipe?

Answer 54

One node at closed end, one antinode at open end.

Question 55

Frequency of first harmonic in closed pipe?

Answer 55

f = v/4L.

Question 56

What type of wave is sound?

Answer 56

Longitudinal mechanical wave.

Question 57

What does sound require to travel?

Answer 57

A medium.

Question 58

What determines pitch of sound?

Answer 58

Frequency.

Question 59

What determines loudness of sound?

Answer 59

Amplitude.

Question 60

What determines timbre (quality) of sound?

Answer 60

Waveform and harmonics.

Question 61

Speed of sound in air (room temp)?

Answer 61

≈343 m/s.

Question 62

How does temperature affect sound speed?

Answer 62

Higher temperature increases speed.

Question 63

Why can’t sound travel through space?

Answer 63

No particles to transmit vibrations.

Question 64

What type of waves are EM waves?

Answer 64

Transverse waves of oscillating electric and magnetic fields.

Question 65

Do EM waves require a medium?

Answer 65

No, they travel through vacuum.

Question 66

Speed of all EM waves in vacuum?

Answer 66

3.0×10⁸ m/s.

Question 67

EM spectrum (longest → shortest λ)?

Answer 67

Radio, Microwave, Infrared, Visible, UV, X-ray, Gamma.

Question 68

Which EM waves are ionising?

Answer 68

UV, X-rays, Gamma rays.

Question 69

What changes when EM waves enter a new medium?

Answer 69

Wavelength changes, frequency constant.

Question 70

Highest energy EM wave?

Answer 70

Gamma rays.

Question 71

Lowest frequency EM wave?

Answer 71

Radio waves.

Question 72

What is polarisation?

Answer 72

Restricting wave oscillations to a single plane.

Question 73

Which waves can be polarised?

Answer 73

Only transverse waves.

Question 74

What happens when light passes through two polarising filters at 90°?

Answer 74

No light passes.

Question 75

Uses of polarisation?

Answer 75

Sunglasses, photography, stress analysis, LCD screens.

Question 76

What is the Doppler effect?

Answer 76

Apparent change in frequency due to relative motion between source and observer.

Question 77

When source moves toward observer, frequency...?

Answer 77

Appears higher.

Question 78

When source moves away, frequency...?

Answer 78

Appears lower.

Question 79

Example of Doppler effect in daily life?

Answer 79

Changing pitch of ambulance siren.

Question 80

Astronomical use of Doppler effect?

Answer 80

Measuring redshift of galaxies.

Question 81

Define intensity (I).

Answer 81

Power per unit area, I = P/A.

Question 82

Relationship between intensity and amplitude?

Answer 82

I ∝ A².

Question 83

What happens to intensity when distance doubles (point source)?

Answer 83

Intensity becomes one quarter (inverse square law).

Question 84

What is the decibel scale used for?

Answer 84

Measuring sound intensity level.

Question 85

Formula for sound level in decibels?

Answer 85

L = 10 log₁₀(I/I₀).

Question 86

What does Huygens’ principle explain?

Answer 86

Reflection, refraction, diffraction.

Question 87

What is resonance?

Answer 87

Large amplitude oscillations when driven at natural frequency.

Question 88

Example of resonance?

Answer 88

Tuning forks, bridges, MRI.

Question 89

What is damping?

Answer 89

Reduction in amplitude due to energy loss.

Question 90

What is a forced oscillation?

Answer 90

Oscillation caused by an external periodic force.

Question 91

Apparatus to measure wavelength of sound?

Answer 91

Resonance tube or oscilloscope setup.

Question 92

How to observe stationary waves on a string?

Answer 92

Vibration generator and signal generator setup.

Question 93

How to measure wavelength of light?

Answer 93

Using a diffraction grating.

Question 94

Diffraction grating equation?

Answer 94

d sinθ = nλ.

Question 95

Effect of more slits in diffraction grating?

Answer 95

Maxima become sharper and brighter.

Question 96

Laser safety precaution?

Answer 96

Avoid direct eye exposure.

Question 97

Wave reflection from a fixed boundary?

Answer 97

Inverts (phase change of π).

Question 98

Wave reflection from a free boundary?

Answer 98

No phase change.