A slit of width a is illuminated by white light. For red light (λ = 6500 Å), the first minima is obtained at θ = 30°. Then the value of a will be 

(1) 3250 Å

(2) 6.5 × 10^–4 mm

(3) 1.24 microns

(4) 2.6 × 10^–4 cm

A parallel monochromatic beam of light is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of the incident beam. At the first minimum of the diffraction pattern, the phase difference between the rays coming from the edges of the slit is:
1. \(0\)
2. \(\dfrac \pi 2 \)
3. \(\pi\)
4. \(2\pi\)

The angle of polarisation for any medium is \(60^\circ,\) what will be the critical angle for this?

A beam of light AO is incident on a glass slab (μ = 1.54) in a direction as shown in figure. The reflected ray OB is passed through a Nicol prism on viewing through a Nicole prism, we find on rotating the prism that, 

1. the intensity is reduced down to zero and remains zero.
2. the intensity reduces down some what and rises again.
3. there is no change in intensity.
4. the intensity gradually reduces to zero and then again increases.

In the propagation of electromagnetic waves, the angle between the direction of propagation and plane of polarisation is:

(1) 0^o

(2) 45^o

(3) 90^o

(4) 180^o

An unpolarised light incident on a polariser has amplitude \(A\), and the angle between analyzer and polariser is \(60^{\circ}\). The light transmitted by the analyzer has an amplitude of:
1. \(A\sqrt{2}\)
2. \(\frac{A}{2\sqrt{2}}\)
3. \(\frac{\sqrt{3}A}{2}\)
4. \(\frac{A}{2}\)

When an unpolarized light of intensity I₀ is incident on a polarizing sheet, the intensity of the light which does not get transmitted is:
1. Zero
2. \(I_0\)
3. \(\dfrac{I_0}{2}\)
4. \(\dfrac{I_0}{4}\)

When the angle of incidence on a material is 60°, the reflected light is completely polarized. The velocity of the refracted ray inside the material is (in ms^–1)

1. 3 × 10⁸

2. $\left(\frac{{\displaystyle 3}}{{\displaystyle \sqrt{2}}}\right)\times {10}^8$

3. $\sqrt{3}\times {10}^8$

4. 0.5 × 10⁸

Two polaroids are placed in the path of unpolarized beam of intensity I₀ such that no light is emitted from the second polaroid. If a third polaroid whose polarization axis makes an angle θ with the polarization axis of first polaroid, is placed between these polaroids then the intensity of light emerging from the last polaroid will be:

(1) $\left(\frac{{\displaystyle I_0}}{{\displaystyle 8}}\right){\sin }^{2}2\theta$

(2) $\left(\frac{{\displaystyle I_0}}{{\displaystyle 4}}\right){\sin }^{2}2\theta$

(3) $\left(\frac{{\displaystyle I_0}}{{\displaystyle 2}}\right){\cos }^4\theta$

(4) $I_0{\cos }^4\theta$

In the adjacent diagram, CP represents a wavefront and AO & BP, the corresponding two rays. What would be the condition on θ for constructive interference at P between the ray BP and reflected ray OP?

(1) cosθ = 3λ/2d

(2) cosθ = λ/4d$\theta$

(3) secθ – cosθ = λ/d

(4) secθ – cosθ = 4λ/d