Waves Equations (ch. 4)

Question 1

Constructive interference path difference (general)

Answer 1

nλ

Question 2

Destructive interference path difference (general)

Answer 2

(n+1/2)λ

Question 3

Transmitted intensity of polarised light incident on a polariser (Malus’ law)

Answer 3

Iₒ cos² T

Question 4

Fringe spacing in double slit diffraction

Answer 4

λD/d (where D = distance from slits to screen and d = distance between slits)

Question 5

Constructive interference for thin film interference (conditions for bright fringe with 1 inversion)

Answer 5

2dn = (m+½)λ

Question 6

Speed of a wave

Answer 6

fλ

Question 7

Period

Answer 7

1/f

Question 8

Intensity and amplitude (relationship)

Answer 8

I∝A² or I = kA²

Question 9

Intensity and distance from source (relationship)

Answer 9

I ∝ D^−2 or I = k/D^2

Question 10

Angle of incidence at which reflected light is totally polarized (Brewster’s angle)

Answer 10

tan(θ) = n2/n1 (where n1 = refractive index of material wave travels in, n2 = refractive index of material wave’s reflected from)

Question 11

Period of a pendulum

Answer 11

T = 2π√(l/g)

Question 12

Period of a mass-spring

Answer 12

T = 2π√(m/k)

Question 13

Velocity of a point in SHM

Answer 13

v = ω√(x0^2 - x^2)

Question 14

Snell’s law

Answer 14

n1/n2 = sin(θ2)/sin(θ1) = v2/v1

Question 15

Path difference in double slit diffraction (draw diagram)

Answer 15

Path difference = d sin(θ)

Question 16

General acceleration in SHM

Answer 16

a0 = -ω^2x0

Question 17

Basics of refractive index

Answer 17

n = c/v

Question 18

Transmitted intensity of non-polarised light incident on a polariser

Answer 18

1/2 initial intensity

Question 19

Maximum velocity in SHM

Answer 19

v=ωx0

Question 20

Transmitted intensity of non-polarised light through a polariser

Answer 20

I=1/2I0

Intensity is halved