One day on a spacecraft corresponds to $2$ days on the earth. The speed of the spacecraft relative to the earth is
$1.5 \times {10^8}m{s^{ - 1}}$
$2.1 \times {10^8}m{s^{ - 1}}$
$2.6 \times {10^8}m{s^{ - 1}}$
$5.2 \times {10^8}m{s^{ - 1}}$
Two monochromatic beams $A$ and $B$ of equal intensity $I$, hit a screen. The number of photons hitting the screen by beam $A $ is twice that by beam $ B$. Then what inference can you make about their frequencies ?
The number of photons emitted by a $10\,watt$ bulb in $10\,second,$ if wavelength of light is $1000\,\,\mathop A\limits^o ,$ is
The energy of a photon of light of wavelength $450 nm$ is
A caesium photocell, with a steady potential difference of $60V$ across, is illuminated by a bright point source of light $50 cm$ away. When the same light is placed 1m away the photoelectrons emitted from the cell