Assertion : Corpuscular theory fails in explaining the velocities of light in air and water.
Reason : According to corpuscular theory,light should travel faster in denser medium than in rarer medium.

$A$ source of light emits a continuous stream of light energy which falls on a given area. Luminous intensity is defined as

Assertion: The colour of the green flower seen through red glass appears to be dark.
Reason: Red glass transmits only red light.

$A$ laser beam can be focused on an area equal to the square of its wavelength. $A$ $He-Ne$ laser radiates energy at the rate of $1 \, mW$ and its wavelength is $632.8 \, nm$. The intensity of the focused beam will be:

Two point monochromatic and coherent sources of light of wavelength $\lambda$ are placed on the dotted line in front of a large screen. The sources emit waves in phase with each other. The distance between $S_1$ and $S_2$ is $d$,while their distance from the screen is much larger. Then,
$(1) \rightarrow$ If $d = 7\lambda / 2$,$O$ will be a minima.
$(2) \rightarrow$ If $d = 4.3\lambda$,there will be a total of $8$ minima on the $y$-axis.
$(3) \rightarrow$ If $d = 7\lambda$,$O$ will be a maxima.
$(4) \rightarrow$ If $d = \lambda$,there will be only one maxima on the screen.
Which is the set of correct statements?

The intensity of light from a continuously emitting laser source operating at $638 \,nm$ wavelength is modulated at $1 \,GHz$. The modulation is done by momentarily cutting the intensity off with a frequency of $1 \,GHz$. What is the farthest distance apart two detectors can be placed in the line of the laser light,so that they can see the portions of the same pulse simultaneously?
(Consider the speed of light in air $c = 3 \times 10^{8} \,m/s$)