In a diffraction pattern due to single slit of width a, the first minimum is obsrved at an angle 30^o when light of wavelength  is incident on the slit. The first secondary maximum is observed at an angle of:

• sin^-1 (2/3)

• sin^-1 (1/2)

• sin^-1 (3/4)

• sin^-1 (3/4)

On observing light from three different stars P, Q and R, It was found that intensity of violet colour is maximum in the spectrum of P, the intensity of green colour is maximum in the spectrum of R and the intensity of red colour is maximum in the spectrum of Q. If T_P, T_Q and T_R are the respective absolute temperature of P, Q and R, then  it can conclude from the above observations that

• T_P > T_Q>T_R
  

• T_P > T_R> T_Q

• T_P > T_R < T_Q

• T_P > T_R < T_Q

In a double slit experiment, the two slits are 1 mm apart and the screen is placed in 1 m away. A monochromatic light of wavelength 500nm is used. What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of double slit within the central maxima of single slit pattern?

• 0.2mm

• 0.1 mm

• 0.5 mm

• 0.5 mm

For a parallel beam of monochromatic light of wavelength 'λ'diffraction is produced by single slit whose width 'a' is of the order of the wavelength of the light. If 'D' is the distance of the screen from the slit the width of the central maxima will be

• 2Dλ/a

• Dλ/a

• Da/λ

• Da/λ

When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts as a plane sheet of glass. This implies that the liquid must have refractive index

• equal to that of glass

• less than one

• greater than that of glass

• greater than that of glass

A beam of light of  = 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is,

• 1.2 cm

• 1.2 mm

• 2.4 cm

• 2.4 cm

In the young's double slit experiment, the intensity of light at a point on the screen (where the path difference is ) is K. The intensity at a point where the path difference is  will be,

• K

• K/4

• K/2

• K/2

A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from 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 decrease

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

120.

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