41.

A monochromatic beam of light is used for the formation of fringes on the screen by illuminating the two slits in the Young's double slit interference experiment. When a thin film of mica is interposed in the path of one of the interfering beams then

• the fringe width increases

• the fringe width decreases

• the fringe width remains the same but the pattern shifts

• the fringe pattern disappears

An object is immersed in fluid. In order that the object becomes invisible, it should

• behave as  perfect reflector

• absorb all light falling on it

• have refractive index one

• have refractive index exactly matching with that of the surrounding fluid

Carbon dating is best suited for determining the age of fossils if their age in years is of the order of

• 10⁸

• 10⁴

• 10⁴

• 10⁶

An endoscope is employed by a physician to view the internal parts of a body organ. It is based on the principle of

• refraction

• reflection

• total internal reflection

• dispersion

We wish to see inside an atom. Assuming the atom to have a diameter of  100 pm, this means that one must be able to resolve a width of say 10 pm. If an electron microscope is used, the minimum electron energy required is about

• 1.5 keV

• 15 keV

• 150 keV

• 1.5 keV

When a compact disc is illuminated by a source of white light, coloured lines are observed. This is due to

• dispersion

• diffraction

• interference

• refraction

The dependence of binding energy per nucleon, B_A  on the mass number A, is represented by

Which logic gate is represented by the following combination of logic gates?

• OR

• NAND

• AND

• NOR

A Ge specimen is doped with Al. The concentration of acceptor atoms is  ∼ 10²¹ atoms/m³. Given that the intrinsic concentration of electron-hole pairs is  ∼ 10¹⁹/m³, the concentration of electrons in the speimen is

• 10¹⁷/m³

• 10¹⁵/m³

• 10⁴/m³

• 10²/m³

Assertion:  A red object appears dark in the yellow light.

Reason: The red colour is scattered less.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false