23.Radiation from hydrogen gas excited to first excited state is used for
illuminating certain metallic plate. When the same plate is exposed to the radiation from some unknown hydrogen like gas excited to the same level
it is found that de-Broglie wavelength of fastest photoelectron has
decreased by 2.3 times. It is given that energy corresponding to longest
wavelength of Lyman series of the unknown gas is 3 times the ionization
energy of hydrogen gas (13.6????????). The work function (in ????????) of the
metallic plate is [???????????????? (2.3)2 = 5.25]

24. Shown in figure is a block at rest having an inclined smooth groove in vertical plane. The horizontal surface is smooth. A ball of same mass as that of block at rest is released from top end. The time when ball will leave groove is nL 2g3 Find n. 60 25.A flying disc of radius r is moving with constant speed vo while rotating anticlockwise with angular speed along a curve PQ as shown below. Radius of curvature of curve at the instant is 4r. The magnitude of acceleration of point A at the instant is 3v nr Find n.