This question has a paragraph followed by two statements, Statement $$-1$$ and Statement $$-2$$. Of the given four alternatives after the statements, choose the one that describes the statements.

A thin air film is formed by putting the convex surface of a plane-convex lens over a plane glass plane. With monochromatic light, this film gives an interference pattern due to light, reflected from the top (convex) surface and the bottom (glass plate) surface of the film.

Statement - $$1$$ : When light reflects from the air-glass plate interface, the reflected wave suffers a phase change of $$\pi .$$

Statement - $$2$$ : The center of the interference pattern is dark.

This question has Statement - $$1$$ and Statement - $$2$$. Of the four choices given after the statements, choose the one that best describes the two statements.
Statement -$$1$$ : Sky wave signals are used for long distance radio communication. These signals are in general, less stable then ground wave signals.
Statement -$$2$$ : The state of ionosphere varies from hour to hour, day to day and season to season.

Energy required for the electron excitation in $$L{i^{ + + }}$$ from the first to the third Bohr orbit is :

This question has Statement - $$1$$ and Statement - $$2$$. Of the four choices given after the statements, choose the one that best describes the two statements.

Statement - $$1$$ : A metallic surface is irradiated by a monochromatic light of frequency $$v > {v_0}$$ (the threshold frequency). The maximum kinetic energy and the stopping potential are $${K_{\max }}$$ and $${V_0}$$ respectively. If the frequency incident on the surface is doubled, both the $${K_{\max }}$$ anmd $${V_0}$$ are also doubled.
Statement - $$2$$ : The maximum kinetic energy and the stopping potential of photoelectrons emitted from a surface are linearly dependent on the frequency of incident light.