I WANT PHYSICS

INTRODUCTION TO ELECTRICITY ELECTRICITY: Electricity is a branch of physics which deals with study of charges. The property of matter that is responsible for electrical phenomena is called charge. Electricity is further divided into two sub branches. They are: 1)     Static electricity: the study of charges which are at rest. And 2)     Current electricity: study of charges under motion. This is what we are also calling as electric current. In terms of electric current materials are classified into three types: 1)     Conductors: the materials which can able to allow electric current to pass through them. Eg: all metals, water with salts and minerals, etc. 2)     Insulators: the materials which cannot able to allow electric current to pass through them. Eg: wood, plastic, rubber, etc. 3)     Semi conductors: the materials which cannot allow electric current freely as conductors. These materials can able to allow only a partial current to flow slowly through them. Eg: silicon, germanium

 HUMAN EYE AND COLOURFUL WORLD EXAMPLE QUESTIONS:   1  1)  Light of wavelength λ 1 enters a medium with refractive index n 2 from a medium with refractive index n 1 . What is the wavelength of light in second medium? ANS:   we know, refractive index is inversely proportional to wavelength.             n∞1/ λ ð n 1 /n 2 = λ 2 / λ 1 ð λ 2 =n 1 λ 1 /n 2   2  2)   If a white sheet of paper is stained with oil, the paper turns transparent. Why? ANS: we can get so many answers for this question because there may be multiple reasons for this. But i will suggest one best answer for this. A white sheet of paper consists of cellulose. The refractive index of cellulose is very near to the refractive index of oil. so, it turns transparent.   3    3)  A light ray falls on one of the faces of a prism at an angle 40 o so that it suffers angle of minimum deviation of 30 o . Find the angle of prism and angle of refraction at the given surface. ANS: To answer this quest

  SCATEERING OF LIGHT   Atoms or molecules which are exposed to light absorb light energy and emit some part of the light energy in different directions. This is the basic process happens in scattering of light.   The effect of light on a molecule or an atom depends on the size of atom or molecule. If the size of the particle (atom or molecule) is small, it will be affected by higher frequency (lower wave length) light and vice versa.   Actually we can see different colours because of scattering of light. When molecular size (of the molecules of an object) are comparable to wave length of a particular colour then that object will scatter that particular colour.  Let us observe some examples in the nature.   BLUE COLOUR OF SKY   We know that our atmosphere contains different types of molecules and atoms. The reason for blue sky is due to the molecules N 2 and O 2 . The sizes of these molecules are comparable to the wavelength of blue light. These molecules act as scat

  DISPERSION: The splitting of white light into different colours (VIBGYOR) is called Dispersion . When a white light is sent through a prism with some angle with the surface, it splits into seven different colours.   We can consider that white light is a collection of waves with different wavelengths. Violet colour is known to have the shortest wavelength while red is of the longest wavelength.     According to wave theory, light can be thought of a wave propagating in all directions. Light is an electromagnetic wave. Here no particle physically oscillates back and forth. Instead, the magnitude of electric and magnetic fields, associated with the electromagnetic wave, vary periodically at every point. These oscillating electric and magnetic fields propagate in all directions with the speed of light.   The reason lies in the fact that, while the speed of light is constant in vacuum for all colours, it depends on the wav

  PRISM:   A prism is a transparent medium separated from the surrounding medium by at least two plane surfaces which are inclined at a certain angle in such a way that, light incident on one of the plane surfaces emerges from the other plane surface. Consider a triangular glass prism. It contains  two triangular bases and three rectangular plane lateral surfaces. These lateral surfaces are inclined to each other. Let us consider that triangle PQR represents outline of the prism where it rests on its triangular base.       Let us assume that a light ray is incident on  the plane surface PQ of a prism at M as shown in figure. Draw a perpendicular to the surface at M. It becomes a normal to that surface. The angle between the incident ray and normal is called angle of incidence (i 1 ). The ray is refracted at M. It moves through prism and meets the other plane surface at N and finally comes out of the prism. The ray which comes out of the surface PR at N is called emergent ray . Dra