The transition from the state $n=3$ to $n=1$ in a hydrogen-like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from:

$A$ closed hollow insulated cylinder is filled with gas at $0^{\circ} C$ and also contains an insulated piston of negligible weight and negligible thickness at the middle point. The gas in one side of the piston is heated to $100^{\circ} C$. If the piston moves $5 ~cm$,the total length of the hollow cylinder is: (in $~cm$)

Which of the following is an accessory whorl of a flower?

In $DNA$,the complementary bases are

If the lines $x^2+2xy-35y^2-4x+44y-12=0$ and $5x+\lambda y-8=0$ are concurrent,then $\lambda$ equals

Half-life of a radioactive substance is $20 \, min$. The difference between the time when it is $33 \%$ disintegrated and $67 \%$ disintegrated is approximately ......... $min$.