## Monday, October 12, 2009

### IIT JEE Physics Final Revision Set 46

1. The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately:
(A) 540 nm (B) 400 nm
(C) 310 nm (D) 220 nm

2. X-rays are produced in an X-ray tube operating at a given accelerating voltage. The wavelength of the continuous X-rays has values from :
(A) 0 to ∞
(B) λmin to ∞ where λmin > 0
(C) 0 to λmax where λmax < ∞
(D)λmin to λmax where 0 < λmin < λmax < ∞

3. A particle of mass m is executing oscillations about the origin on the x-axis. Its potential energy is U(x) = k |x|³ where k is a positive constant. If the amplitude of oscillation is a, then its time period T is :

(A) proportional to 1/√a
(B) proportional of a
(C) proportional to √a
(D) proportional to a³

Paragraph for 4 and 5

A particle of mass 10-2 Kg is moving along the positive x-axis under the influence of a force F(x) = – (k/2x²) where k = 10-2 Nm². At time t = 0 it is at x = 1.0 m and its velocity is v = 0:

4. Find its velocity when it reaches x = 0.5 m
5. Find the time at which it reaches x = 0.25 m

Source 1998 JEE