Wave Optics — Physics STD 12 Science — Question

As per this diagram a point charge +q is placed at the origin O. Work done in taking another point charge -Q  from the point A [co-ordinates (0, a) ] to another point B [co-ordinates (a, 0)] along the straight path AB is

(a) Zero

(b)

(c)

(d)

A barometer kept in an elevator reads 76cm when it is at rest. If the elevator goes up with increasing speed, the reading will be:

1. zero.
2. 76cm.
3. < 76cm.
4. > 76cm.

In an electric heater 4 amp current passes for 1 minute at potential difference of 250 volt, the power of heater and energy consumed will be respectively

(a) 1 kW, 60 kJ

(b) 0.5 kW, 30 kJ

(c) 10 kW, 600 kJ

(d) None of these

By corpuscular theory of light, the phenomenon which can be explained is

(a) Refraction

(b) Interference

(c) Diffraction

(d) Polarisation

A string of negligible thickness is wrapped several times around a cylinder kept on a rough horizontal surface. A man standing at a distance 1 from the cylinder holds one end of the string and pulls the cylinder towards him. There is no slipping anywhere. The length of the string passed through the hand of the man while the cylinder reaches his hands is:

1. l
2. 2l
3. 3l
4. 4l

A double convex lens of glass of m = 1.5 has radius of curvature of each of its surface is 0.2 m.  The power of the lens is

(a) + 10 dioptres

(b) – 10 dioptres

(c) – 5 dioptres

(d)  +5 dioptres

The current between B and D in the given figure is

(a) 1 amp

(b) 2 amp

(c) Zero

(d) 0.5 amp

A cell of internal resistance r is connected to an external resistance R. The current will be maximum in R, if:

A point charge is kept at the centre of metallic insulated spherical shell. Then: