Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

The radius of a wavefront as the waves propagate:

The relation between n₁ and n₂, if behaviour of light rays is as shown in figure is

(a)

(b)

(c)

(d)

Assertion : The electrical conductivity of earth’s atmosphere decrease with altitude.

Reason     : The high energy particles (i.e. g-rays and cosmic rays) coming from outer space and entering our earth’s atmosphere causes ionisation of the atoms of the gases present there and the pressure of gases decreases with increase in altitude.

(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 assertion is false but reason is true.

Hydrogen atom excites energy level from fundamental state to n = 3. Number of spectral lines according to Bohr, is?

A copper wire of length 1 m and radius 1 mm is joined in series with an iron wire of length 2 m and radius 3 mm and a current is passed through the wires. The ratio of the current density in the copper and iron wires is

(a) 18 : 1

(b) 9 : 1

(c) 6 : 1

(d) 2 : 3

In a diode AM-detector, the output circuit consist of R = 1kW and C = 10 pF. A carrier signal of 100 kHz is to be detected. Is it good

(a) Yes	(b) No
(c) Information is not sufficient	(d) None of these

For measuring voltage of any circuit, potentiometer is preferred to voltmeter because:

The stopping potential is directly related to:

Advantage of optical fibre

(a) High bandwidth and EM interference

(b) Low bandwidth and EM interference

(c) High band width, low transmission capacity and no EM interference

(d) High bandwidth, high data transmission capacity and no EM interference