41.

In Young's double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths λ₁ = 12000 $\stackrel{\circ }{\mathrm{A}}$ and λ₂ = 10000 $\stackrel{\circ }{\mathrm{A}}$. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other ?

• 8 mm

• 6 mm

• 4 mm

• 3 mm

A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance froni the slit. If the speed of the electrons is increased, then which of the following statements is correct ?

• Diffraction pattern is not observed on the screen in the case of electrons

• The angular width of the central maximum of the diffraction pattern will increase

• The angular width of the central maximum will decrease

• The angular width of the central maximum will be unaffected

In a n-type semiconductor, which of the following statement is true ?

• Electrons are majority carriers and trivalent atoms are dopants

• Electrons are minority carriers and pentavalent atoms are dopants

• Holes are minority carriers and pentavalent atoms are dopants

• Holes are majority carriers and trivalent atoms are dopants

In a common emitter (CE) amplifier having a voltage gain G, the transistor used has transconductance 0.03 mho and current gain 25. If the above transistor is replaced with another one with transconductance 0.02 mho and current gain 20, the voltage gain will

• $\frac{2}{3} \mathrm{G}$

• 1.5 G

• $\frac{1}{3} \mathrm{G}$

• $\frac{5}{4} \mathrm{G}$

The output (X) of the logic circuit shown in figure will be

• $\mathrm{X} = \stackrel{=}{\mathrm{A}} . \stackrel{=}{\mathrm{B}}$

• $\mathrm{X} = \overline{\mathrm{A} . \mathrm{B}}$

• X = A .B

• $\mathrm{X} = \overline{\mathrm{A} + \mathrm{B}}$

The output (X) of the logic circuit shown in figure will be

• $\mathrm{X} = \stackrel{=}{\mathrm{A}} . \stackrel{=}{\mathrm{B}}$

• $\mathrm{X} = \overline{\mathrm{A} . \mathrm{B}}$

• X = A .B

• $\mathrm{X} = \overline{\mathrm{A} + \mathrm{B}}$