We do not see an interference pattern when light from two identical electric bulbs falls on a white wall. Give reasons.

What is interference of light? Write two essential conditions for sustained interference pattern to be produced on the screen. Why interference pattern is not detected when two coherent sources are far apart?

What are coherent source of light? Why no interference pattern is observed when two coherent source are too close

• Take a thick sheet of cardboard and make a small hole or narrow slit in its middle. • Allow sunlight to fall on the narrow slit. This gives a narrow beam of white light. • Now, take a glass prism and allow the light from the slit to fall on one of its faces as shown in Fig. • Turn the prism slowly until the light that comes out of it appears on a nearby screen. What do you observe? You will find a beautiful band of colours.

GIVE REASONS - WHY : Objects are not seen clearly when we enter from bright light to a room with dim light.

Two groups (A and B) of bean plants of similar sizes and same leaf area were placed in identical conditions. Group A was exposed to light of Wavelength 400-450 nm and Group B to light of wavelength of 500-550 nm. Compare the photosynthetic rate of the two groups giving reason.

GIVE REASONS - WHY : We do not see the actual position of the stars.