IIT JEE and NEET Physics @ Venkats Academy

Light is a form of energy. It exhibits a wide variety of properties. If the size of the object is much larger than the wavelength of the light, light appears like travelling in straight lines. It exhibits certain properties under these conditions and that properties are studied and rename called Ray optics.

In Ray optics we study about reflection, refraction, dispersion and the deviation.

Reflection is the phenomena of light bouncing back into the same medium after striking a boundary that is separating the two media.

Refraction is the phenomenon of light due to which light travels into the other medium after striking a boundary that is separating the two media.

Dispersion is the phenomenon of splitting up of a white light into multiple colors when it is passed through a prism.

Deviation is the phenomena of changing its path when the light is passing through a different media.

In this chapter we are also going to study regarding mirrors, lenses, prisms, critical angle, total internal reflection, microscopes and telescopes.

This post is a list of all the topics in Ray optics which includes problems and solutions.

Ray Optics Introduction and Reflection of Light

Sign Convention and Image Tracing of Light in Ray Optics

Problems and Solutions on Refraction of Light

Refraction of Light and Snell's Law

Problems and solutions on Refraction of Light

Normal Shift and Lateral Shift due to Refraction of Light

Problems on normal shift Refraction of Light

Critical Angle and Total Internal Reflection

Applications of Total Internal Reflection

Problems and Solutions on Critical angle and Total internal Reflection

Refraction of Light Through Curved Surfaces

Power and Focal Length of a Lens

Refraction of Light Through Prism

Problems and Solutions on Refraction of Light Through Prism

Angular Dispersion and Dispersive Power

Problems on Angular Dispersion and Dispersive Power

Working of Human Eye and Simple Microscope

Working of Compound microscope

Working of a Galilean Telescope

Other Complete Lessons in this blog includes

Units and Dimensions

One and Two Dimensional Motion

Mechanical Properties of Matter

Heat and Thermodynamics

Waves and Oscillations

Wave Optics

Semi Conductor Devices

Dual nature of Radiation and Matter

Power of a lens

It is the measure of ability to produce a convergence or divergence of parallel light rays of light. It is mathematically the reciprocal of focal length of a lens. We can express the power of a lens in terms of meters as well as centimeters as shown below.

If a portion of the light that is striking the lens is obstructed, the image formed by the lens will have less intensity but of same focal length.

If a lens is immersed in a medium whose refractive index is less than that of the material of the lens, the nature of the lens remains the same.

If a lens is immersed in a medium whose refractive index is more than the refractive index of the material of the lens, the nature of the lens will be reversed. It means a convex lens in this case behaves like a concave lens and vice versa.

If a lens is immersed in a medium whose refractive index is equal to the refractive index of material of the lens, the lens behaves like a plain glass and its focal length will become infinite.

When a lens is cut parallel to its principal axis, its focal length refractive index and radius of curvature remains the same. But the intensity of the image formed is reduced.

When a lens is cut perpendicular to the principal axis, it’s curved nature decreases and hence focal length increases. But the intensity of the image will be the same.

We can write the formula for the effective focal length and the effective power of a lens as shown below.

Problem and solution

A air lens with equal radius of curvature of 10 cm is cut in the glass cylinder as shown. Determine the focal length and the nature of the air lens. If the liquid of refractive index 2 is filled in the lens, what will happen to the focal length of the lens and how does the nature of the lens will change?

We can find the focal length of the lens using the lens makers formula. Basing an answer, we can confirm that the air lens behaves like diverging lens. When the air bubble is filled with the liquid of refractive index 2, the nature of the lens will be reversed and it behaves like a converging lens of the same focal length. The detailed solution is given below.