51.

In an interference, the intensity of two interfering waves are  I  and  4I  respectively. They produce intensity at two points A and B with phase angle of  $\raisebox{1ex}{$\mathrm{\pi }$}\!\left/ \!\raisebox{-1ex}{$2$}\right.$ and  $\mathrm{\pi }$ respectively. Then difference in between them is

• I

• 2 I

• 4 I

• 5 I

In a single slit diffraction with k = 500 nm and lens of diameter 0.1 mm then width of central maxima, obtain on screen at a distance of 1 m will be

• 5 mm

• 1 mm

• 10 mm

• 2.5 mm

Assertion:  When white light fall on the compact disc, multicolours are seen after reflection. 

Reason: CD disc behaves like a prism.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion:  If objective and eye lenses of a microscope are interchanged then it can work as telescope. 

Reason:  The objective lens of telescope has  small focal length.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false.

In  Young's  double  slit experiment, the  two  slits  act  as coherent  sources  of  equal  amplitude  $\mathrm{\alpha }$  and  of  wavelength  λ. In  another  experiment  with  the  same  set  up,  the two  slits  are  sources  of  equal  amplitude  $\mathrm{\alpha }$  and  wavelength  λ, but  are  incoherent. The  ratio  of  intensities  of  light  at  the  midpoint  of  the  screen  in  the  first  case  to  that  in  the  second  case  is

• 2 : 1

• 1 : 2

• 3 : 4

• 4 : 3

In Young's double slit experiment, the distance between two slits is made three times then the fridge width will become

• 9 times

• 1/9 times

• 3 times

• 1/3 times

Light  is  incident  normally  on  a  diffraction  grating  through  which  the  first  diffraction  is seen  at 32°. In  this  case  the  second  order  diffraction will  be

• at 80^o

• at 64^o

• at 48^o

• there is no second order diffraction

Assertion: A white source of light during interference forms only white and black fringes.

Reason: Width of fringe is inversely proportional to the wavelength of the light used.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

If a  street light of mass Mis suspended from the end of a uniform rod of length L in different possible patterns as shown in figure, then

• pattern A is more sturdy

• pattern B is more study

• pattern C is more sturdy

• all will have same sturdiness

Assertion:  Standard optical diffraction gratings cannot be used for discriminating between different X-ray wavelengths. 

Reason: The grating spacing is not of the order of X-ray wavelengths.

• If both assertion and reason are true and reason is the correct explanation of the assertion

• If both assertion and reason are true but reason is not the correct explanation of the assertion

• If assertion is true, but reason is false

• Both assertion and reason are false statements