51.

A beam of light composed of red and green rays is incident obliquely at a point on the face of a rectangular glass slab. When coming out on the opposite parallel face, the red and green rays emerge from.

• Two points propagating in two different non- parallel directions.

• Two points propagating in two different parallel directions

• one point propagating in two different directions.

• one point propagating in the same direction.

The plane face of a plano-convex lens is silvered. If μ be the refractive index and R, the radius of curvature of the curved surface, then the system will behave like a concave mirror of curvature.

• μR

• R²/μ

• R/(μ -1)

• [(μ + 1)/(μ-1)]R

The maximum numbers of possible interference maxima for slit separation equal to twice the wavelength in Young's double slit experiment is

• infinite

• five

• three

• zero

An isotropic point source of light is suspended h metre vertically above the centre of the circular table of radius r metre. Then, the ratio of illumenances at the centre to that at the edge of the table is

• $1 + \left(\frac{{\mathrm{r}}^2}{{\mathrm{h}}^2}\right)$

• $1 + \left(\frac{{\mathrm{h}}^2}{{\mathrm{r}}^2}\right)$

• ${\left\{1 + \frac{{\mathrm{r}}^2}{{\mathrm{h}}^2}\right\}}^{3/2}$

• ${\left\{1 + \frac{{\mathrm{h}}^2}{{\mathrm{r}}^2}\right\}}^{3/2}$

The half-life period of a radioactive element X is the same as the mean life of another radioactive element Y. Initially, both of them have the same numbers of atoms then,

• X and Y have the same decay rate initially

• X and Y decay at the same rate always

• Y will decay at a faster rate than X

• X will decay at a faster rate than Y

A source emits electromagnetic waves of wavelength 3m. One beam reaches the observer directly and other after reflection from a water surface, travelling 1.5 m extra distance and with an intensity reduced to 1/4 as compared to intensity due to the direct beam alone. The resultant intensity will be.

• (1/4) fold

• (3/4) fold

• (5/4) fold

• (9/4) fold

The following circuit represents

• OR gate

• XOR gate

• AND gate

• NAND gate

The mass of a proton is 1847 times that of an electron. An electron and a proton are injected into a uniform electric field at right angle to the direction of the field with the same initial K.E.

• The electron trajectory will be less curved than the proton trajectory.

• both the trajectories will be straight

• the proton trajectory will be less curved than the electron trajectory.

• both the trajectories will be equally curved.

A photocell is illuminated by a small bright source placed 1m away. When the same source of light is placed 2m away, the electrons emitted by photo cathode

• Carry one quarter of their previous energy

• carry one quarter of their previous momenta

• are half as numerous

• are one quarter as numerous

The potential of an atom is given by V = V₀loge(r/r₀) where r₀ is a constant and r is the radius of the orbit. Assuming Bohr's model to be applicable, which variation or r_n with n is possible (n being a principal quantum number)?

• ${\mathrm{r}}_{\mathrm{n}} \propto \mathrm{n}$

• ${\mathrm{r}}_{\mathrm{n}} \propto \frac{1}{\mathrm{n}}$

• ${\mathrm{r}}_{\mathrm{n}} \propto {\mathrm{n}}^2$

• ${\mathrm{r}}_{\mathrm{n}} \propto \frac{1}{{\mathrm{n}}^2}$