VARIOUS PHENOMENA BASED ON

ATMOSPHERIC REFRACTION

CLASS 10TH LOTUS

GROUP NUMBERGROUP MEMBERSAKASH SHARMABHARAT DANISHHARSH RAJPUTHARSHIT MEMORIAROHIT BATRASIDDHANT GUPTA

ACKNOWLEDGEMENTI would like to thank my Science

teacher Shalini Mam and my group members for helping me in making

this presentation. My group members helped me in editing of this

presentation. My parents helped me in formatting the matter of the presentation. I collected the

information from the internet and from some books.My other gratitude I would like to convey to my school who suggest me to make this and to have marks for adding it into examination.

CONTENTREFRACTIONCAUSES OF REFRACTIONLAWS OF REFRACTION OF LIGHTATMOSPHERIC REFRACTIONTWINKLING OF STARSADVANCED SUNLIGHT AND DELAYED SUNSETRAINBOW FORMATIONSCATTERING OF LIGHTWHY THE SKY IS BLUEWHY THE SUN APPEARS RED AT SUNRISE AND SUNSETWHY THE CLOUDS APPEAR WHITE

REFRACTIONThe change in the direction of light when it

passes from one medium to another, is called Refraction of light.

In other words, the bending of light when it goes from one medium to another

obliquely is called Refraction of light-

CAUSE OF REFRACTION OF LIGHT

The refraction of light is due to the change in the speed of light on going

from one medium to another.

Greater the difference in the speeds of light in the two media, greater will be

the amount of refraction of light.

LAWS OF REFRACTIONThe refraction of light on going from one medium to another takes place from one medium to another takes place according to two laws which are known as Laws of

Refraction. These are:-The incident ray, the normal ray, and the

point of incidence, all lie in the same plane.The ratio of sine of incidence to the sine of

refraction is a constant for the light of a given colour and for the given pair of

media. This is also known as Snell’s Law of refraction.

If i is angle of incidence and r is the angle of refraction, then

Sin i/ sin r = constant

ATMOSPHERIC REFRACTION

In the Atmosphere we have several layers having different optical densities.

The refraction of light caused by earth’s atmosphere having layers of air of varying

optical densities is called Atmospheric Refraction.

TWINKLING OF STARSThe twinkling of stars is due to the atmospheric

refraction of star’s light. When the light coming from a star enters the earth’s

atmosphere, It undergoes refraction due to the varying optical densities of air at various altitudes. The continuously changing atmosphere refracts the light from the stars by different amounts from one

moment to the next. The star light reaching our eyes increases and decreases continuously due to

atmospheric refraction. And the star appears to twinkle at night.

ADVANCE SUNRISE AND DELAYED SUNSET

When the sun is slightly below the horizon, then the sun’s light coming from less dense air to more dense air is refracted downwards as it passes to

the atmosphere. Because of this atmospheric refraction, the sun appears to be raised above the horizon when actually it is below the horizon. The

same is in the case of delayed sunset.It is due to the atmospheric refraction, we see the sun

for 4 minutes extra.

The raindrops in the atmosphere act like many small prisms. When

sunlight enters a rain drop, it

refracts inside the drop. Then it strikes the

boundary between two media (which is known as total

internal reflection) and disperses.

This light is reflected off backside of

raindrop at critical angle. It takes many different raindrops to

produce a rainbow.

RAINBOW FORMATION

SCATTERING OF LIGHT

Scattering of light occurs when light is deflected in all directions. Scattering of light occurs when

light bounces on colloidal particle and particles large than colloidal particles. It is also called Tyndall

effect. Blue skies and red suns are due to scattering of light.

WHY THE SKY IS BLUEThe sunlight is made

up of seven colours. When sunlight passes

through the atmosphere, most of the lights of longer

wavelengths such as red, yellow, orange etc. present in it do

not scattered much by air molecules and

hence pass straight through. However the shorter wavelengths scattered all around

the sky by air molecules in the

atmosphere.That is why the sky

appears blue.

WHY SUN APPEARS RED AT SUNRISE AND

SUNSETThe sun and the

surrounding sky appear red at sunrise and sunset because

at that time most of the

blue colour has been scattered out and away from our eyes, leaving behind

mainly red colour in the

direct sunlight beam that

reaches our eyes.

WHY THE CLOUDS APPEAR WHITE

When the particles are

large, the scattering of

light cause the particles to be look as white.

Some light penetrates to

cloud base and white light is

scattered in all directions.

That is why cloud appears as white

THANK YOU