Light of wavelength 6000 $\stackrel{\circ }{\mathrm{A}}$ falls on a single slit of width 0.1 mm. The second minimum will be formed for the angle of diffraction of

• 0.08 rad

• 0.06 rad

• 0.012 rad

• 0.15 rad

In a double slit experiment, the screen is placed at a distance of 1.25 m from the slits. When the apparatus is immersed in water (µ_w = 4/3), the angular width of a fringe is found to be 0.2°. When the experiment is performed in air with same set up, the angular width of the fringe is

• 0.4°

• 0.27°

• 0.35°

• 0.15°

63.

Two piano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contact with their curved surfaces towards each other and the space between them is filled with liquid of refractive index $\frac{4}{3}$. Then the combination is 

• convex of focal length 70 cm

• concave of focal length 70 cm

• concave of focal length 66.6 cm

• convex of focal length 66.6 cm

When a metallic surface is illuminated by a light of wavelength λ, the stopping potential for the photoelectric current is 3 V. When the same surface is illuminated by light of wavelength 2λ, the stopping potential is 1 V, the threshold wavelength for this surface is

• 4 λ

• 3.5 λ

• 3 λ

• 2.75 λ

The temperature at which protons in proton gas would have enough energy to overcome Coulomb barrier of 4.14 x 10^-14 J is (Boltzmann constant = 1.38 x 10^-23 JK^-1)

• 2 × 10⁹ K

• 10⁹ K

• 6 × 10⁹ K

• 3 × 10⁹ K

The activity of a radioactive element decreases to one-third of the original activity A₀ in a period of 9 yr. After a further lapes of 9 yr, its activity will be

• A₀

• $\frac{2}{3}{\mathrm{A}}_0$

• $\frac{{\mathrm{A}}_0}{9}$

• $\frac{{\mathrm{A}}_0}{6}$

Two nucleons are at a separation of 1 fermi. The net force between them is F₁ if both are neutrons, F₂ if both are protons and F₃ if one is proton and the other is a neutron. Then

• F₁ > F₂ > F₃

• F₁ = F₃ > F₂

• F₂ > F₁ > F₃

• F₁ = F₂ > F₃

The truth table for the following logic circuit is

• $\left|\begin{array}{ccc}\mathrm{A}& \mathrm{B}& \mathrm{Y}\\ 0& 0& 0\\ 0& 1& 1\\ 1& 0& 1\\ 1& 1& 0\end{array}\right|$

• $\left|\begin{array}{ccc}\mathrm{A}& \mathrm{B}& \mathrm{Y}\\ 0& 0& 0\\ 0& 1& 1\\ 1& 0& 1\\ 1& 1& 1\end{array}\right|$

• $\left|\begin{array}{ccc}\mathrm{A}& \mathrm{B}& \mathrm{Y}\\ 0& 0& 1\\ 0& 1& 0\\ 1& 0& 1\\ 1& 1& 0\end{array}\right|$

• $\left|\begin{array}{ccc}\mathrm{A}& \mathrm{B}& \mathrm{Y}\\ 0& 0& 1\\ 0& 1& 1\\ 1& 0& 0\\ 1& 1& 1\end{array}\right|$

In the operation of n-p-n transistor compared to that of a triode, the p base acts as

• emitter

• cathode

• grid

• plate

In the diagram, the input AC is across the terminals A and C. The output across B and D is

• same as the input

• half wave rectified

• zero

• full wave rectified