Neet PYQ 2007

A black body is at $727{}^{\circ }\text{C}$. It emits energy at a rate that is proportional to:

An engine has an efficiency of $1/6$. When the temperature of the sink is reduced by $62{}^{\circ }\text{C}$, its efficiency is doubled. The temperature of the source is:

Monochromatic light of frequency $6.0\times 10^{14}\text{Hz}$ is produced by a laser. The power emitted is $2\times 10^{-3}\text{W}$. The number of photons emitted, on the average, by the source per second is:

For a cubic crystal structure which one of the following relations indicating the cell characteristic is correct?

A common emitter amplifier has a voltage gain of $50$, an input impedance of $100\Omega$ and an output impedance of $200\Omega$. The power gain of the amplifier is: