Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

Assertion :  The energy of charged particle moving in a uniform magnetic field does not change.

Reason    : Work done by magnetic field on the charge is zero.

(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.

A circular loop carrying a current is replaced by an equivalent magnetic dipole. A point on the axis of the loop is in:

For a cell of e.m.f. 2V, a balance is obtained for 50 cm of the potentiometer wire. If the cell is shunted by a  2Ω resistor and the balance is obtained across 40 cm of the wire, then the internal resistance of the cell is

(a) 0.25 Ω

(b) 0.50 Ω

(c) 0.80 Ω

(d) 1.00 Ω

The two slits at a distance of 1 mm are illuminated by the light of wavelength 6.5 . The interference fringes  are observed on a screen placed at a distance of 1m. The distance between third dark fringe and fifth bright fringe will be

(a) 0.65 mm

(b) 1.63 mm

(c) 3.25 mm

(d) 4.88 mm

What determines the hardness of the X-rays obtained from the Coolige tube

(a) Current in the filament

(b) Pressure of air in the tube

(c) Nature of target

(d) Potential difference between cathode and target

Which one of the following is inorganic compound semiconductor?

Which of the transitions in hydrogen atom emits a photon of lowest frequency  (n = quantum number)

(a) n = 2 to n = 1

(b) n = 4 to n = 3

(c) n = 3 to n = 1

(d) n = 4 to n = 2

A biconvex lens forms a real image of an object placed perpendicular to its principal axis. Suppose the radii of curvature of the lens tend to infinity. Then the image would

(a) Disappear

(b) Remain as real image still

(c) Be virtual and of the same size as the object

(d) Suffer from aberrations

Current provided by a battery is maximum when

(a) Internal resistance equal to external resistance

(b) Internal resistance is greater than external resistance

(c) Internal resistance is less than external resistance

(d) None of these

The angle of polarisation for any medium is 60^o, what will be critical angle for this

(a)

(b)

(c)

(d)