Ray Optics and Optical Instruments — Physics STD 12 Science — Question

A charge of   is placed on each of the 64 identical drops of radius 2cm. They are then combined to form a bigger drop. Find its potential             

(a) 7.2

(b) 7.2

(c) 1.44

(d) 1.44

A point object is placed at a distance of 30cm from a convex mirror of focal length 30cm. The image will form at:

1. Infinity.
2. Pole.
3. Focus.
4. 15cm behind the mirror.

The electron emitted in beta radiation originates from:

A slit of width a is illuminated by white light. For red light (λ = 6500 Å), the first minima is obtained at θ = 30°. Then the value of a will be

(a) 3250 Å

(b) 6.5

(c) 1.24 microns

(d) 2.6

The radius of the Bohr orbit in the ground state of hydrogen atom is 0.5 Å. The radius of the orbit of the electron in the third excited state of   will be

(a) 8 Å

(b) 4 Å

(c) 0.5 Å

(d) 0.25 Å

A charged particle enters in a uniform magnetic field with a certain velocity. The power delivered to the particle by the magnetic field depends on:

The chemical equivalent of silver is 108. If the current in a silver voltameter is 2 Amp., the time required to deposit 27 grams of silver will be

(a) 8.57 hrs

(b) 6.70 hrs

(c) 3.35 hrs

(d) 12.50 hrs

If a comb is rubbed on dry hairs, and then brought near paper pieces, it:

The effective resistance of two resistors in parallel is .  If one of the resistors is disconnected the resistance becomes 4 W.  The resistance of the other resistor is

(a) 4 W

(b) 3 W

(c)

(d)