Optics Flashcards
The path of light is called ray of light group of these rays are called
Beam of light
Some of the sources emit thier own light and they are called
Luminous object
You make the light from a torch to fall on your eyes, will you able to see the object
No, we can see the object only when the light is made to fall on the object and the light reflected from the object is viewed by our eyes
Properties of light
1 Light is a form of energy
2 light always travels along the straight line
3) light does not need any medium for propagation. it can even travel through vacuum
4) the speed of light in vacuum or air is 3*10^8 m/s
5) light is in the form of waves, it is characterized by a wavelength [lambda (h)] and frequency we which are related by the following equation; c =vh c - velocity of light
6 Different coloured light has different wavelength and frequency
7 among the visible lights, violet light has the lowest wavelength and red light has the highest wavelength
8 when light is incident on the interface between two media it is partly reflected and partly refracted
Refraction of light
When a Ray of light travels from one transparent medium into another obliquely , the path of the light undergoes deviation. This deviation of race of light is called refraction.
Refraction take place due to the difference in the velocity of light in different media
The velocity of light is more in a rare medium and less In a denser medium
Frist Law of refraction
The incident ray the refractory of light and the normal to the refracting surface all lie in the same plane
Second law of refraction
The ratio of the sine of the angle of incidence and sign of the angle of refraction is equal to ratio of refractive indices of the two media. This law is also known as snell’s law
Sin i/ sin r=u2/u1
_______ gives us an idea of how fast are how slow light travels in a medium(second law of refraction)
Refractive index
Refractive index
The ratio of speed of light in vacuum(c) to the speed of light in a medium (v) is defined as refractive index (u) of the medium
u= c/v
Second law of refraction
The speed of light in a medium is low if the refractive index of the medium is high and vice versa
When light travels from here then sir medium into a rare medium, the refracted ray is bent away from the normal drawn to the interface
When light travels from a rare medium into denser medium, the refractor ray is Bent toward the normal drawn to the interface
If you have source of light produces a light of single colour it is known as
Monochromatic source
Source of light produces a white light which contain light of different colour is known as
Composite source
Eg: Sunlight, Mercury vapour lamp
Dispersion of light
When a beam of white light or composite lens light is refracted through any transparent media such as glass or water, it is split into its component colour. This phenomenon is called as dispersion of light
The band of colors is termed as
Spectrum
The spectrum consists of VIBGYOR
Why do we get the spectrum when white light is refracted by a transparent medium
This is because different coloured light are bent through different angles. that is the angle of refraction is different for different colour
angle of refraction is the smallest for red and highest for violet
Assertion: snell’s law we know that the angle of refraction is determined in term of the refractive index of the medium
Hence, the refractive index of the medium is different for different coloured light. This indicates that the refractive index of a medium is dependent on the wavelength of the light
scattering of light
When sunlight enters the earth’s atmosphere, the atom and molecule of different gases present in the atmosphere refract the light in all possible directions this is called as scattering of light
In this phenomenon the beam of light is redirected in all directions when it interacts with a particle of medium. The interacting particle of the medium is called scatterer
Types of scattering
Elastic scattering
Inelastic scattering
Elastic scattering
If the energy of incident beam of light and scattered beam of light are same then it is called as elastic scattering
Inelastic scattering
If the energy of them incident beam of light and be the scatter the beam of light or not same then it is called inelastic scattering
Types
Rayleigh scattering
Mei scattering
Tyndall scattering
Raman scattering
Rayleigh scattering
The scattering of light by the atom or molecules of the gas in the earth atmosphere is known as Rayleigh scattering
Rayleigh scattering law
Rayleigh’s scattering law states that, the amount of scattering of light is inversely proportional to the 4th power of it wavelength
→ proportional
S →1/h⁴. h- wavelength
According to this law the shorter wavelength colours are scattered much more than the longer wavelength colours
Scattering causes the sky to appear in blue colour
When sunlight passes through the atmosphere, the blue colour (shorter wavelength) is scattered to a greater extent than the red colour ( longer wavelength)
The colour of the sun is red at sunrise and sunset
At sunrise and sunset the light rays from the sun have to travel long distance in the atmosphere then at noon. Hence, most of the blue lights are scatter away and only the red light which in get reached scatter reaches us
Mei scattering
Mie scattering take place when the diameter of the scatterer is similar to or larger than the wavelength of the incident light. It is also an elastic scattering. The amount of catering is independent of wavelength
Mie scattering is caused by pollen, dust, smoke, water droplets, and other particles in the lower portion of the atmosphere
Mie scattering Is responsible for the white appearance of the clouds
When white light falls on the water drop, all the colours are equally scattered which together form the white light
Tyndall scattering or Tyndall effect
The scattering of light rays by the colloidal particles in the colloidal solution is called Tyndall scattering or Tyndall effect
When a beam of sunlight, enters into a dusty room through a window, then its path becomes visible to us
This is because, tiny dust particles present in the air of the room scatter the beam of light
Colloid
Colloid is a microscopically small substance that is equally dispersed throughout another material
Eg milk, ice cream, muddy water, smoke
Raman’s scattering
The interaction of light rays with the particles of pure liquid or transparent solids which leads to a change in wavelength or frequency
In Raman scattering , when a parallel beam of ________ light passes through a gas or liquid or transparent solid, a part of light rays are scattered
Monochromatic or single colored
In Raman scattering , when a parallel beam of monochromatic (single colored) light passes through a gas or liquid or transparent solid, a part of light rays are scattered
The scattered light contains some additional frequency or wavelength other than that of incident frequency or wavelengths. This is known as raman’s catering or Raman effect
The spectral lines having frequency equal to the incident ray frequency is called
Rayleigh line
Spectral lines which are having frequencies other than the incident ray frequency are called
Raman line
The line having frequency lower than the incident frequency is called stoke line
The lines having frequently higher than the incident frequency are called anti stoke lines
Lens bounded by whose spherical surface such that it is thicker at the centre than at the edge. A beam of light passing through it, is converged to a point
Convex or bi convex lens
Convex lens are also called as converging lens
Lens bounded by two spherical surfaces such that it is thinner at the centre than at the edges. A beam of light passing through it, is diverged spread out to a point
Concave or bi concave lens
Concave lens is also called as diverging lens
If one of the faces of a bi convex lens is plane, it is known as
Plano convex lens
If one of the faces of a bi concave lens is plane, it is known as
Plano concave lens
It is an optically transparent medium bounded by two spherical refracting surfaces or one plane and one spherical surface
Lens
Images formed due to refraction through a convex and the concave lens
Rule1: when a Ray of light strike the convex or concave lens obliquely at its optical centre, it continuous to follow it path without any deviation
Rule 2 when rays parallel to the principal Axis strikes a convex or concave lens the refracted ray are converged to(convex) or appears to diverge from (concave lens) the principal focus
Rule 3 when a ray passing through (convex lens) or directed toward (concave lens) the principle focus strikes a convex or concave lens the refracted ray will be parallel to the principal axis
Refraction through a convex lens
When an object is placed at infinity
Images formed at principal focus
The size of the images much smaller than that of the object
Refraction through a convex lens
When an object is placed behind the centre of curvature
Ya real and inverter image is formed between the centre of curvature and principle focus
The size of the images smaller than that of object
Refraction through a convex lens
When when an object is placed at the centre of curvature
A real and inverted image is formed at the other centre of curvature
The size of the image is the same as that of object
Refraction through a convex lens
When an object is placed in between the centre of curvature and principle focus
Real and inverted image is formed Behind the centre of curvature
The size of the images bigger than the object
Refraction through a convex lens
When an object is placed at the focus
Real images is formed at infinity
The size of the images much larger than that of the object
Refraction through a convex lens
When an object is placed in between principal focus and optical centre
Virtual images formed
the size of the images larger than that of
Application of convex lens
Camera lenses magnifying lenses ,microscope ,telescope, slide projector
They are used to correct the defect of vision called hypermetropia
