Wave Optics

In young's double-slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths λ₁ = 12000 A and λ₂ =10000 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 fringes from the other?

• 8 mm

• 6 mm

• 4 mm

• 4 mm

Which of the following is not due to total internal reflection ?

• Difference between apparent and real depth of a pond

• Mirage on hot summer days

• Brilliance of diamond

• Brilliance of diamond

Two slits in  Young's experiment have widths in the ratio 1:25.The ratio of intensity at the maxima and minima in the interference pattern I_max/I_min is

• 9/4

• 121/49

• 49/121

• 49/121

On the first minimum adjacent to the central maximum of a single slit diffraction pattern, the phase  difference between the Huygens wavelet from the edge of the slit and the wavelet from the midpoint of the slit is

• π/4 radian

• π/2 radian

• π radian

• π radian

The speed of light in media M₁ and M₂ is 1.5 x 10⁸ m /s respectively. A ray of light enters from medium M₁ and M₂ at incidence angle i. If the ray suffers total internal reflection the value of i is 

• equal to sin^-1 (2/3)

• equal to or less than sin^-1 (3/5)

• equal to or greater than sin^-1 (3/4)

• equal to or greater than sin^-1 (3/4)

Two periodic waves of intensities I₂ and I₂ pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is 

• I₁ + I₂

• 
• 
• 

A boy is trying to start a fire by focusing sunlight on a piece of paper using an equal convex lens of focal length 10 cm. The diameter of the sun is 1.39 x 10⁹ m  and its mean distance from the earth is 1.5 x 10¹¹ m. What is the diameter of the sun's image on the paper?

• 9.2 x 10^-4 m

• 6.5 x 10^-4 m

• 6.5 x 10^-5 m

• 6.5 x 10^-5 m

Two points are located at a distance of 10 m and 15 m from the source of oscillation. The period of oscillation is 0.05 s and the velocity of the wave is 300 m/s. What is the phase difference between the oscillation of two points?

• π/3

• 2π/3

• π

• π

Two Polaroids P₁ and P₂ are placed with their axis perpendicular to each other. Unpolarised light I0 is incident on P₁. A third polaroid P₃
is kept in between P₁ and P₂ such that its axis makes an angle 45^o with that of P₁. The intensity of transmitted light through P₂ is

• I₀/2

• I₀/3

• I₀/8

• I₀/8

Unpolarised light is incident from air on a plane surface of a material of refractive index 'µ'. At a particular angle of incidence 'i', it is found that the reflected and refracted rays are perpendicular to each other. Which of the following options is correct for this situation?

• Reflected light is polarised with its electric vector parallel to the plane of incidence

• Reflected light is polarised with its electric vector perpendicular to the plane of incidence

• i = tan^-1( 1/μ )

• i = sin^-1( 1/μ )