Wave Optics — Physics STD 12 Science — Question

A capacitor with air as the dielectric is charged to a potential of  100 volts. If the space between the plates is now filled with a dielectric of dielectric constant 10, the potential difference between the plates will be

(a) 1000  volts

(b) 100 volts

(c) 10 volts

(d) Zero

de Broglie relation is true  for:

A slit of size 0.15 cm is placed at 2.1 m from a screen. On illuminated it by a light of wavelength 5 × 10^–5 cm. The width of central maxima will be

(a) 70 mm

(b) 0.14 mm

(c) 1.4 mm

(d) 0.14 cm

The plane faces of two identical plano-convex lenses each having focal length of 40 cm are pressed against each other to form a usual convex lens. The distance from this lens, at which an object must be placed to obtain a real, inverted image with magnification one is

(a) 80 cm

(b) 40 cm

(c) 20 cm

(d) 162 cm

The oscillating electric and magnetic vectors of an electromagnetic wave are oriented along

(a) The same direction but differ in phase by 90°

(b) The same direction and are in phase

(c) Mutually perpendicular directions and are in phase

(d) Mutually perpendicular directions and differ in phase by 90°

Assertion  :   X-rays can penetrate through the flesh but not through the bones.

Reason      : The penetrating power of X-rays depends on voltage.

(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.

Two wires A and B of same material and same mass have radius 2rand r. If resistance of wire A is 34 Ω, then resistance of B will be

(a) 544 Ω

(b) 272 Ω

(c) 68 Ω

(d) 17 Ω

Statement-I : Energy is released when heavy nuclei undergo fission or light nuclei undergo fusion and

Statement-II: For heavy nuclei, binding energy per nucleon increases with increasing Z. while for light nuclei it decreases with increasing Z.