A Problem from Optics – Reflection of light

Convex and concave mirrors have same radii of curvature R. The distance between the mirrors is 2R. At what point on the common optical axis of the mirrors should a point source of light A be placed for the rays to converge at the point A after being reflected first on the convex and then […]

lenses OPTICS Plus Two Physics

Numerical Problems from Light

Madhu sent us the following problems from “Light”. Visitors can attempt to solve the problems by quoting the question number. Most of the questions below are based on mirror formula and lens formula.   Mirror Formula   Lens Formula   Now try solving these questions/problems. If in doubt or not able to solve the problems, […]

Answers Ask Physics combination f3 focal length focal lengths Interesting Questions length lenses OPTICS Project thin lenses Young

A Numerical from Combination of thin lenses in contact

Two thin lenses of focal lengths f1=20cm and f2=60cm are placed in contact. find the focal length f3 of the combined lenses. find also the focal length f of a third lens placed in contact with these two that would result in overall focal length f11=-40cm. (Asked Young)
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Ask Physics Interesting Questions OPTICS

Why can’t we see through opaque objects?

Why can’t we see through opaque objects? What is the reason? (Kavya asked) Answer: When light falls on an object, a part of it is absorbed, another part transmitted and the rest reflected. Surfaces have different abilities for these. Substances which do not transmit any light are opaque. Incoming search terms:what are the possibilities of […]

Ask Physics mechanism of propagation of light OPTICS

What accounts for the acceleration or deceleration of light when it travels from one medium to another?

“When light passes through different mediums speed changes but who provide acceleration to change velocity?” This question was posted by Jishnu Answer: Just imagine you are participating in a cross country race. When the road is good you can travel faster; but if the path is a marshy place, your speed will decrease. This is …Read the full post


Interference is in complete agreement to law of conservation of energy

Tilak gurjar posted; “Interference is in complete agreement to law of conservation of energy. Comment” Answer: If there were no interference, the resultant intensity at a point illuminated by two sources will be I = I1+I2 Due to interference This shows that energy is conserved even after interference. There is only a redistribution of energy. There […]