Wave Optics — Physics STD 12 Science — Question

Consider the motion of the tip of the minute hand of a clock. In one hour:

1. The displacement is zero.
2. The distance covered is zero.
3. The average speed is zero.
4. The average velocity is zero.

Consider the following statements regarding series grouping of capacitors and select the correct statements.

1. Charge on each capacitor remains same and equals to the main charge supplied by the battery.
2. Potential difference and energy distributes in the reverse ratio of capacitance.
3. Effective capacitance is even less than the least of teh individual capacitances.

When the intensity of a light source is increased:

1. The number of photons emitted by the source in unit time increases.
2. The total energy of the photons emitted per unit time increases.
3. More energetic photons are emitted.
4. Faster photons are emitted.

The length of Milky way is

(a) 100,000 light years

(b) 10,000 light years

(c) 1000 light years

(d) 100 light years

The capacities and connection of five capacitors are shown in the adjoining figure. The potential difference between the points A and B  is 60 volts . Then the equivalent capacity between A  and B  and the charge on 5μF  capacitance will be respectively

(a) 44 μF, 300 μC

(b) 16 μF, 150 μC

(c) 15 μF, 200 μC

(d) 4 μF, 50 μC

Light of frequency 8   is incident on a substance of photoelectric work function 6.125eV. The maximum kinetic energy of the emitted photoelectrons is

(a) 17eV

(b) 22eV

(c) 27eV

(d) 37eV

There is 10 units of charge at the centre of a circle of radius 10m. The work done in moving 1 unit of charge around the circle once is

(a) Zero

(b) 10 units

(c) 100 units

(d) 1 unit

Free ²³⁸U nuclei kept in a train emit alpha particles. When the train is stationary and a uranium nucleus decays, a passenger measures that the separation between the alpha particle and the recoiling nucleus becomes x in time t after the decay. If a decay takes place when the train is moving at a uniform speed v, the distance between the alpha particle and the recoiling nucleus at a time t after the decay, as measured by the passenger will be:

1. x + vt
2. x - vt
3. x
4. depends on the direction of the train.

If the current in the circuit for heating the filament is increased, the cutoff wavelength:

The black shapes in the figure are closed surfaces. The electric field lines are in red. For which case the net flux through the surfaces is non-zero?