DP Physics (first assessment 2025)

Question 23M.2.HL.TZ1.3c

Date	May 2023	Marks available	[Maximum mark: 6]	Reference code	23M.2.HL.TZ1.3c
Level	HL	Paper	2	Time zone	TZ1
Command term	Determine, Explain, State	Question number	c	Adapted from	N/A

[Maximum mark: 6]

23M.2.HL.TZ1.3c

(c)

The graph shows the actual variation with displacement $x$ from M of the intensity of the light on the screen. $I_{0}$ is the intensity of light at the screen from one slit only.

(c.i)

Explain why the intensity of light at $x$ = 0 is 4 $I_{0}$ .

[2]

Markscheme

The amplitude «at x = 0» will be doubled ✓

intensity is proportional to amplitude squared / $I$ ∝ A² ✓

(c.ii)

The slits are separated by a distance of 0.18 mm and the distance to the screen is 2.2 m. Determine, in m, the wavelength of light.

[2]

Markscheme

Use of s = $\frac{λ D}{d} \Rightarrow λ$ = $\frac{s d}{D}$ OR s = $\frac{n λ D}{d} \Rightarrow λ$ = $\frac{s d}{n D}$ ✓

$λ$ = « $\frac{0.567 \times 10^{- 2} \times 0.18 \times 10^{- 3}}{2.2}$ =» 4.6 × 10⁻⁷ «m» ✓

(c.iii)

The two slits are replaced by many slits of the same separation. State one feature of the intensity pattern that will remain the same and one that will change.

Stays the same:

Changes:

[2]

Markscheme

Stays the same: Position/location of maxima/distance/separation between maxima «will be the same» / OWTTE ✓

Changes: Intensity/brightness/width/sharpness «of maxima will change»/ OWTTE ✓

Allow other phrasing for maxima (fringes, spots, etc).

Syllabus sections

C. Wave behaviour » C.3 Wave phenomena

Question 23M.2.HL.TZ1.3c

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