Semiconductor Electronic: Material, Devices And Simple Circuits — Physics STD 12 Science — Question

A convex lens of focal length 40 cm is in contact with a concave lens of focal length 25 cm. The power of combination is

(a) – 1.5 D

(b) – 6.5 D

(c) + 6.5 D

(d) + 6.67 D

The primary origin (s) of magnetism lies in:

A charge Q is uniformly distributed over a large plastic plate. The electric field at a point P close to the centre of the plate is 10Vm^-1. If the plastic plate is replaced by a copper plate of the same geometrical dimensions and carrying the same charge Q, the electric field at the point P will become:

In which of the following situations, the heavier of the two particles has smaller de Broglie wavelength? The two particles:

Light of wavelength l = 5000 Å falls normally on a narrow slit. A screen placed at a distance of 1 m from the slit and perpendicular to the direction of light. The first minima of the diffraction pattern is situated at 5 mm from the centre of central maximum. The width of the slit is

(a) 0.1 mm

(b) 1.0 mm

(c) 0.5 mm

(d) 0.2 mm

The molecules in which centres of positive and negative charges coincide are called as:

 Which among the following is the proper way of earthing?

Principle of photoelectric effect was established by :

 The resistivity of certain metals or alloys drops to zero when they are cooled below a certain temperature, this phenomenon is known as __________.