One day on a spacecraft corresponds to $2$ days on the earth. The speed of the spacecraft relative to the earth is
$1.5 \times {10^8}m{s^{ - 1}}$
$2.1 \times {10^8}m{s^{ - 1}}$
$2.6 \times {10^8}m{s^{ - 1}}$
$5.2 \times {10^8}m{s^{ - 1}}$
What is the momentum of a photon having frequency $1.5 \times {10^{13}}Hz$
In a dark room of photography, generally red light is used. The reason is
The minimum intensity of light to be detected by human eye is ${10^{ - 10}}W/{m^2}$. The number of photons of wavelength $5.6 \times {10^{ - 7}}m$ entering the eye, with pupil area ${10^{ - 6}}{m^2}$, per second for vision will be nearly
A photon of wavelength $6630 \ Å$ is incident on a totally reflecting surface. The momentum delivered by the photon is equal to
A beam of electromagnetic radiation of intensity $6.4 \times 10^{-5}\; \mathrm{W} / \mathrm{cm}^{2}$ is comprised of wavelength, $\lambda=310 \;\mathrm{nm} .$ It falls normally on a metal (work function $\varphi=2 \;\mathrm{eV}$ ) of surface area of $1\; \mathrm{cm}^{2} .$ If one in $10^{3}$ photons ejects an electron, total number of electrons ejected in $1 \;s$ is $10^{\mathrm{x}}$.then $\mathrm{x}$ is
$\left(\mathrm{hc}=1240\; \mathrm{eV} \mathrm{nm}, 1\; \mathrm{eV}=1.6 \times 10^{-19} \;\mathrm{J}\right)$