Exam Style Answers 13 Asal Physics CB

 

 

CAMBRIDGE INTERNATIONAL AS & A LEVEL PHYSICS: COURSEBOOK 

Exam-style questions and sample answers have been written by the authors. In examinations, the way marks are awarded may be different.

 Coursebook answers Chapter 13 Exam-style questions 1

B 

2

a

[1]

     t     n     e     m     e     c     a 0      l     p     s      i      D

1

7

separation of slits d  = 5000  = 2.0 × 10−4 cm

 

= 2.0 × 10−6 m 

 First maximum when n = 1: First λ  656 × 10 9  = 0.328   sin θ =  = sin d  2. 0 × 10 6  so, t = sin−1 0.328 = 19.1°  so, −

−

Distanc

[1] [1]

 Second maximum when n = 2: Second  sin θ =  sin

The dashed line represents the resultant wave.  [2]

3

[1]

 

(Your diagram should show a good (Your attempt to sum the two waves.)

b

Wavelength is the same as that of the longer wa wave. ve. 

a b

2λ  d 

=

2 × 656 × 10 2. 0 ×10

9

−

6

=

−

0.656  

[1]

−1

8

 sso, o, θ = sin  0.656 = 41.0°  [1] a Superposition is the algebraic summing of the displacements  [1]  

of two (or more) wa waves. ves. 

[1]

b

 λ =  D  

More rounded 

[1]

 

Even flatter 

[1]

 

leading to λ D 590 ×10 9 ×1.8 ×12 = a =    x 16.8 ×10 3

ax

[1] [1]

−

4

5

6

Radio waves have a long enough wavelength, wa velength, up to 1 km, that they can diffract round the hills. 

[1]

TV  T V waves have very short wavelength (centimetres or millimetres), so cannot diffract round the hills.  a

Using ax ax  = ld  

 

1.5 1.2  = 0.225 m ≈  wavelength λ =  ax  = 8.0 d  0.23 m  [1]  

a = 6.3 × 10−4 m 

c

i

More fringes seen on screen or fringe brightness decreases less from middle to edge of screen  [1]

[1]

 

Less bright 

[1]

[1]

 ii ii

Fringes wider / farther apart  

[1]

 

Same brightness 

[1]

b

 λ; 330 = f  v = f   f   f  × 0.225 

[1]

 

f  = 1470 Hz ≈ 1500 Hz 

[1] [1]

They  T hey gradually go out of phase, and when they are in antiphase, the sound is at its quietest.  [1] The  T he waves waves gradually come back into phase and become loud again.  [1]

1

[1]

 

×

When the waves are in phase, they add up to give loud sound.  

−

9

[1]

a

Coherent: constant phase difference 

[1]

 

Monochromatic: very small or no Monochromatic: range of wa wavelengths/frequencies velengths/frequencies 

[1]

b  

i

First order produced by waves with path difference of one wavelength wavelength  [1] Second order produced by waves wa ves with path difference of two wavelengths 

[1]

Cambridge International AS & A Level Physics – Sang, Jones, Chadha & Woodside © Cambridge University Press 2020

   

CAMBRIDGE INTERNATIONAL AS & A LEVEL PHYSICS: COURSEBOOK 

11 a

 ii ii

Any two from:

 

Lines at end A are further apart or  lines at end B are closer together  [1]

 

Lines at end A are thinner or lines at end B are wider  [1]

 

Lines at end A are brighter or lines at end B are dimmer   [1]

 iii iii

n λ = d  sin  sin θ 

Spreading out of a wave after passing through a gap in a barrier   [1]

 

or around an object 

b

i, ii and iii

[1]

[1] ο

sin 19.5 2  × 10

 

n = 1, leading to λ = 5000

 

λ = 6.68 × 10−7 ≈ 6.7 × 10−7 m 

 iv iv

sin θ =  nDl  leading to

[1] [1] 0 min

sin θ  = 2 × 6.68 × 10−7 × 5000 × 102  [1]  θ = 41.8

10 a

[1]

 

to give (nearly) zero resultant. 

[1]

b

 λ =  ax  leading

 

  [1]   12.5 10 2 number of fringes in 45 cm distance = 

D 1.2 × 1.5 × 10 2

1

[1]

The superposition of two waves waves 180° out of phase 

=

to x = Dal   

 

−

×

[1]

 

Three maxima 

[1]

c

 λ leading to f  c = f   f  to f  =  3. 0

 

f  = 2.0 × 1010 Hz 

−

108   1. 5 × 10 2 ×

 

−

[1]

One mark for each line (the min line and the 1 line can be above the central line) 

−

45 × 10 2  = 3.125  x  

2

° ≈ 42° 

c

[3]

ax  λ =  D  

[1] 10 2 × 12 × 10 2   60 × 10 2 −

−

 

leading to = 18

 

λ = 3.6 × 10−2 m (or 3.6

×

−

cm) 

[1] [1]

[1]

Cambridge International AS & A Level Physics – Sang, Jones, Chadha & Woodside © Cambridge University Press 2020