Aberrations; a lecture in Optics. 4

Optical systems are studied under two assumptions

object point does not lie far away from the axis of the optical system.

rays taking part in image formation make a small angle with the axis of the optical system.

The domain of optics where above two assumptions are valid is called as Paraxial optics. Paraxial systems are highly idealized and in reality do not perfectly represent the situation. The consequential errors in image reconstruction are known as aberrations.
The paraxial assumption can be represented by truncating at the first term of the polynomial expansion of the sin function by the Maclaurin series. More…

This year’s Nobel prize in Chemistry. Reply

What happens when some UV falls on biological molecules? (or any kind) some of these molecules like the wooden pole absorb the energy and there still remains energy which they can emit as visible light. So the UV light kicks the molecules and the molecules in turn emit visible light. This implies that the UV wavelength that the molecules absorbed energy at are very small compared to the wavelength at which they emit visible light. This is always the case.

When we say some materials are fluorescent it means they absorbed higher energy and emitted lower energy radiations of colorful light.

But this has a great deal of application apart from its theoretical interest. More…

How summer and winter occur ! A preliminary note. Reply

Yes it is indeed winter but you wouldn’t know until the sun sets when suddenly there is a cool feeling. The day weather is still not very cool. The abrasiveness is caused by the direct glares and flares from sun which are instantly cut off when sun sets and the equilibrium conditions are felt. Plus remember that the seasons are not due to the distance of earth from sun, between maximum and minimum, the earth varies its distance only by 3.4%. The season are due to what are called the “obliquity of ecliptic” that is; The inclination of earth in its Orbital Plane of sun (maxm; 23.44 degree).

During a variation of inclination of earth the sun also changes its relative distance from above a point on earth, causing what we call as season. In scientific terms we say seasons are effected due to equinoxes and sub-solar points or solstices. All together there are 4 of these points for a place on earth per year. SO any point on earth will have 2 equinoxes and 2 solstices. More…

Perihelionic Winters ! Reply

Winter and Summer are occurring counter intuitively due to valuation in a day long configuration of earth and sun. A few million kms distance change from sun isn’t causing the season, but how exactly we are tilted even at the shortest distance from sun can cause winter. And this stands to change over 26000 years, twice, so winter will sometimes occur due to how we are tilted to the sun, even if we will be farthest away from it, but we won’t be there to experience it. More…

Interesting planetary facts ! Reply

Mars winter and summer would have a wider variation due to Sun’s relative distance being a 17%; variation in radiation is 34% (2 x 17%)

For earth since distance of earth and sun varies from maximum to minimum within 3.4% the variation in sun’s radiation energy is 2×3.4 = 6.8%

Also Venus is far more closer to Earth in most of its actual parameters. (eg inclinations don’t matter, mass and gravity and pressure etc do) But Venus is 31 times hotter than earth on an average and a person would feel 100 times more pressure from the atmosphere above his head. He would burn and crack like a f** fish. More…

A particle that defies classical mechanics ! 1

A photon has no mass but energy and it has speed and it has momentum although it does not have mass. Thats impossible in Classical Mechanics. Because Classical Mechanics associates with every mass; momentum and kinetic and potential energy. All those would be zero if mass were to be zero.

Also the speed of the photon is constant while its energy and momentum are changing. This is unimaginable in classical mechanics. In CM first momentum can’t be defined from mass and speed if mass is zero, then while speed is not changing how is momentum changing? So both variables speed and mass fail to define a momentum for the photon, and not just the failure to have a mass. How then momentum is defined for this particle? Its not defined as long as photon is just a particle. Thats impossible. More…