AQA A-level Physics Double Slit Interference Mark Scheme

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Mark schemes
A
1 [1]

C
2 [1]

B
3 [1]

A
4 [1]

B
5 [1]

B
6 [1]

C
7 [1]

D
8 [1]

(a) w = λD/s
9
C1

correct substitution – condone wrong powers of ten

C1

cao 11(.3) mm or equivalent; unit required

A1
3

(b) same frequency or wavelength

C1

constant phase (relationship)

A1
2
[5]




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(a) λ = yd/D
10
C1



substitution correct: condone

powers of 10

C1

5.6 × 107 m

A1
3

(b) waves arrive out of phase (with each other)

B1

path difference is 1.5λ

B1

idea of cancellation/destructive interference/negative
interference destruction

B1
3
[6]




(a) constant phase relationship (1) (1)
11 [or same frequency (wavelength) (1) and same phase difference (1)]
2

(b) S1R = 15cm on diagram (1) =75cm ∴ 30 waves (1)
S2R = 16cm on diagram (1) = 80cm ∴ 32 waves (1)
2 whole waves difference so in phase at R (1) maximum (1)
max 5

(c) (falls then rises to) maximum at Q (1)
(then falls and rises to) maximum at P (1)
2




(d) = = 1.2 × 1010 Hz (or 12 GHz) (1)
1
[10]

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