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

Assertion  :  If a charged particle is moving on a circular path in a perpendicular magnetic field, the momentum of the particle is not changing,.
Reason     : Velocity of the particle in not changing in the magnetic field.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

The distance between an object and the screen is 100 cm. A lens produces an image on the screen when placed at either of the positions 40 cm apart. The power of the lens is(a) ≈ 3 dioptres(b) ≈ 5 dioptres(c) ≈ 7 diopters(d) ≈ 9 diopters

An electromagnetic waves can be produced, when charge is:

 The electrostatic potential on the perpendicular bisector due to an electric dipole is _____________.

The velocity of a particle is zero at t = 0.

1. The acceleration at t = 0 must be zero.
2. The acceleration at t = 0 may be zero.
3. If the acceleration is zero from t = 0 to t = 10s, the speed is also zero in this interval.
4. If the speed is zero from t = 0 to t = 10s the acceleration is also zero in this interval.

A person cannot see distinctly at the distance less than one metre. Calculate the power of the lens that he should use to read a book at a distance of 25 cm(a) + 3.0 D(b)  + 0.125 D(c) – 3.0  D(d)  + 4.0 D

A potentiometer having the potential gradient of 2 mV/cm is used to measure the difference of potential across a resistance of 10 ohm. If a length of 50 cm of the potentiometer wire is required to get the null point, the current passing through the 10 ohm resistor is (in mA)(a) 1(b) 2(c) 5(d) 10

In a transformer, the number of turns in primary coil and secondary coil are 5 and 4 respectively. If 240 V is applied on the primary coil, then the ratio of current in primary and secondary coil is

Energy conversion in a photoelectric cell takes place from(a) Chemical to electrical(b) Magnetic to electrical(c) Optical to electrical(d) Mechanical to electrical

Electromotive Force (EMF) may be defined as: