If ilm is kept in a wooden box, alpha paritlces from a radiactive source outside the box cannot expose the film but beta particles can. Explain.

A calorimater is kept in a wooden box to insulate it thermally from the surroundings .Why is it neccessery?

A large , heavy box is sliding without friction down a smooth plane of inclination theta . From a point P on the bottom of the box , a particle is projected inside the box . The initial speed of the particle with respect to the box is u , and the direction of projection makes an angle alpha with the bottom as shown in Figure . (a) Find the distance along the bottom of the box between the point of projection p and the point Q where the particle lands . ( Assume that the particle does not hit any other surface of the box . Neglect air resistance .) (b) If the horizontal displacement of the particle as seen by an observer on the ground is zero , find the speed of the box with respect to the ground at the instant when particle was projected .

At the suggestion of Earnest Rutherford, hans Geiger and ernest Marsden bombarded a thin gold foil by alpha -particles from a polonium source. It was expected that alpha -particles would go right through the foil with hardly any deflection. Although, most of the alpha particles indeed were not deviated by much, a few were scattered through veryi large angles. Some were even scattered in the backward direction. The nly way to explain the results, rutherford found, was to picture an atom as being compoed of a tiny nucleus in which its positive charge and nearly all its mass are concentrated. Scattering of alpha -particles is proportional to target thickness and is inversely proportional to the fourth power of sin((theta)/(2)) , where, theta is scattering angle. Distance of closest approach may be calculated as: r_("min")=(Z_(1)Z_(2)e^(2))/(4piepsi_(0)K) where, K=kinetic energy of alpha -particles. Q. Rutherford's alpha -particle scattering led to the conclusion that:

The cyclotron is a device which is used to accelerate charged particles such as protons, deutrons, alpha particles, etc. to very high energy. The principle on which a cyclotron works is based on the fact that an electric field can accelerate a charged particle and a magnetic field can throw it into a circular orbit. A particle of charge +q experiences a force qE in an electric field E and this force is independent of velocity of the particle. The particle is accelerated in the direction of the magnetic field. On the other hand, a magnetic field at right angles to the direction of motion of the particle throws the particle in a circular orbit in which the particle revolves with a frequency that does not depend on its speed. A modest potential difference is used as a sources of electric field. If a charged particle is made to pass through this potential difference a number of times, it will acquire an enormous by large velocity and hence kinetic energy. Which of the following cannot be accelerated in a cyclotron?