In the Thomson spectrograph experiment,four positive ions $P, Q, R,$ and $S$ are situated on the $Y-X$ curves as shown in the figure.

If $m$ is the mass of an electron and $c$ is the speed of light,then the ratio of the wavelength of a photon of energy $E$ to the wavelength of an electron of the same energy is:

Energy of an electron and a photon are equal. If the wavelength of the electron is $1\,\mathring{A}$,then the wavelength of the photon is approximately ............. $\mathring{A}$.

The spectrum of an oil flame is an example of:

An electromagnetic wave of wavelength $\lambda$ is incident on a photosensitive surface of negligible work function. If the photoelectrons emitted from this surface have the de-Broglie wavelength $\lambda_{1}$,then:

Given below are two statements:
Statement $I$: Out of microwaves,infrared rays,and ultraviolet rays,ultraviolet rays are the most effective for the emission of electrons from a metallic surface.
Statement $II$: Above the threshold frequency,the maximum kinetic energy of photoelectrons is inversely proportional to the frequency of the incident light.
In the light of the above statements,choose the correct answer from the options given below: