Which one of the following gases is liberated when ethyl alcohol is heated with methyl magnesium iodide?

The angle of elevation of an object from a point $P$ on the level ground is $\alpha$. Moving $d$ metres on the ground towards the object,the angle of elevation is found to be $\beta$. Then the height (in metres) of the object is

If the length of a stretched string is shortened by $40\%$ and the tension is increased by $44\%$,then the ratio of the final and initial fundamental frequencies is

Which of the following is an essential amino acid?

The major product of the reaction is :

In the Davisson and Germer experiment,the velocity of electrons emitted from the electron gun can be increased by