Question

25-29

50 Sound A0:12 25 Plane sound waves of wavelength 0.12 m are incident on two narrow slits in a box with nonreflecting walls, as shown above. At a distance of 5.0m from the center of the slits, a first-order maximum occurs at point P, which is 3.0m from the central maximum. The distance between the slits is most nearly (A) 0.6 m (B) 0.09 m (C) 0.16m (D) 0.20m (E) 0.34 m An electron volt is a measure of (A) energy (B) electric field (D) force per unit electron charge (C) electric potential due to one electron (E) electric charge LAIN E 27. Which graph best shows the maximum kinetic energy of the photoelectrons as a function of the frequency of incident light? 28. When light of unknown frequency shines on a photosensitive material whose work function is 2.5 eV, the maximum kinetic energy of emitted clectrons is 10V. What is the frequency of the incident light? (A) 1.20 X 10" Hz (B) 1.09 X 10 Hz (C)8.45 10" HD) 2.53 X 10% Hz (E) 4.83 x 10 29. Which graph shows the relationship between photon momentum and wavelength? EL "K L

Answer 1

Solution (25) - The correct option is (d) i.e.

d = 0.20 m

Solution (26)- The correct option is (E) i.e.

eV = Electric Chege

Solution (27) - The correct option is (A).

Solution (28) -  The correct option is (C) i.e.

frequency (v) = 8.48 X 10¹⁴ Hz

Solution (29) - The correct option is (D)

The detailed solution is given below-

page no 1

cannot use the X/L Salution (25): Guiven data : Warelength (1) = 0.12m me 1 (first order) AP 1 som 13.0m Sound d= 0.2m Kvé Since the slits are narrow we can use md= dsino we Bu But since o is clearly large small angle approximation from the giren diagram the geometry shows sino = 3/3 Hence, 3 d x 1X0-12 = 5 d= 0.12X5 3 d= 0.20m Hence optim (D) is carret: Solution (26): An electron volt is a measure Electron charge Hence option (E) i carreet sme 0

page no 2

Salution (37) The correct option is (A). Explanation - Below a threshold frequency, there would be no emission and thus zerok for everything below that point: Above the threshold , more frequency means more k based on Graph A hass all K K- hu- with has the constant slope. these properties W: 3.5 ev. Solution (28) : work function maximum Kinetic energy we know the photo eletric equation- K= cloer. K = h 2-0 1:0 era o h2 - 2.5 er 3.5X1.6 X 10-19 J 6.66 10-34 J. See = 0.848 xio's Hz U= 8.48 X 1014 Hz me Hence option (c) es correct. 2

page no 3

Salution (29); as we know that - P: E 튼 h d where in , P- Momentum h= Plank's constant C= speed of light E= Energy da warelength P= h patt The graph between p and it will be rectangular hyperbola Hence cerret graph Hence carreet option is (D). P is- T sme d 3

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