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Date May 2018 Marks available 3 Reference code 18M.2.HL.TZ2.5
Level Higher level Paper Paper 2 Time zone Time zone 2
Command term Sketch Question number 5 Adapted from N/A

Question

Monochromatic light from two identical lamps arrives on a screen.

                                                    M18/4/PHYSI/HP2/ENG/TZ2/05.a_01

The intensity of light on the screen from each lamp separately is I0.

On the axes, sketch a graph to show the variation with distance x on the screen of the intensity I of light on the screen.

[1]
a.

Monochromatic light from a single source is incident on two thin, parallel slits.

M18/4/PHYSI/HP2/ENG/TZ2/05.b_01

The following data are available.

\[\begin{array}{*{20}{l}} {{\text{Slit separation}}}&{ = 0.12{\text{ mm}}} \\ {{\text{Wavelength}}}&{ = 680{\text{ nm}}} \\ {{\text{Distance to screen}}}&{ = 3.5{\text{ m}}} \end{array}\]

The intensity I of light at the screen from each slit separately is I0. Sketch, on the axes, a graph to show the variation with distance x on the screen of the intensity of light on the screen for this arrangement.

[3]
b.

The slit separation is increased. Outline one change observed on the screen.

[1]
c.

Markscheme

horizontal straight line through I = 2

 

M18/4/PHYSI/HP2/ENG/TZ2/05.a

Accept a curve that falls from I = 2 as distance increases from centre but not if it falls to zero.

[1 mark]

a.

«standard two slit pattern»

general shape with a maximum at x = 0

maxima at 4I0

maxima separated by «\(\frac{{D\lambda }}{s}\) =» 2.0 cm

 

Accept single slit modulated pattern provided central maximum is at 4. ie height of peaks decrease as they go away from central maximum. Peaks must be of the same width

M18/4/PHYSI/HP2/ENG/TZ2/05.b/M

[3 marks]

b.

fringe width/separation decreases

OR

more maxima seen

[1 mark]

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Additional higher level (AHL) » Topic 9: Wave phenomena » 9.3 – Interference
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