Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

Which of the following transitions in a hydrogen atom emits photon of the highest frequency

(a) n = 1 to n = 2

(b) n = 2 to n = 1

(c) n = 2 to n = 6

(d) n = 6 to n = 2

The stopping potential V for photoelectric emission from a metal surface is plotted along Y-axis and frequency n of incident light along X-axis. A straight line is obtained as shown. Planck's constant is given by

(a) Slope of the line

(b) Product of slope on the line and charge on the electron

(c) Product of intercept along Y-axis and mass of the electron

(d) Product of Slope and mass of electron

In an insulator, the forbidden energy gap between the valence band and conduction band is of the order of:

In the circuit shown, the value of each resistance is r, then equivalent resistance of circuit between points A and B will be

(a) (4/3) r

(b) 3r / 2

(c) r / 3

(d) 8r/7

The ratio activity of an element becomes 1/64^th of its original value in 60 sec. Then the half life period is

(a) 5 sec

(b) 10 sec

(c) 20 sec

(d) 30 sec

Assertion  :  A narrow pulse of light is sent through a medium. The pulse will  retain its shape as it travels through the medium.

Reason      : A narrow pulse is made of harmonic waves with a large range of wavelengths.

(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.

Which of the following statements given below is not true in the context of magnetic lines of force?

Only paraxial rays are used in image formation by spherical mirror; because this:

To obtain P-type Si semiconductor, we need to dope pure Si  with

(a) Aluminium

(b) Phosphorous

(c) Oxygen

(d) Germanium

If the de Broglie wavelength of a proton is 10⁻¹³m, the electric potential through which it must have been accelerated is: