Question

In a Young's double slit experiment

• A. if a point source is placed symmetrically from both the slits then interference will be observed on the
  screen
• B. if a point source is placed un-symmetrically from both the slits then interference will be observed on the
  screen.
• C. if two slits are illuminated by two independent sources then the interference will be observed on the
  screen.
• D. intensity of light at two slits should be same for better contrast

Answer 1

Answer: (A), (B), (D)

The correct options are
A if a point source is placed symmetrically from both the slits then interference will be observed on the
screen
B if a point source is placed un-symmetrically from both the slits then interference will be observed on the
screen.
D intensity of light at two slits should be same for better contrast

as seen in the image, if a point source is placed symmetrically from both the slits, then interference will be observed on the screen. if the source is placed unsymmetrically, then both slits will receive same type of input, Thus, interference will be observed in this case too. If intensity of light is kept same at both the slits, the darker and brighter patterns will be more contrast. But if the two slits are illuminated by two independent sources, then the darker and the brighter pattern will not be observed because the interference will not be in proper sequence to project it on the screen.