Solve Problems For Combination Of Lenses

We construct image by tracing the rays which emerges from the object and passes through the lenses.

But sometimes image thus formed sustain few defects.

Therefore, to remove such defects we use two or more lenses.

Such type of combination of lenses are called Compound lens. So, let's discuss and solve few problems on Compound lens.

Such type of combination of lenses are called Compound lens. So, let's discuss and solve few problems on Compound lens.

Combination Of Lenses.

The combination can be made either by keeping the lenses in contact or by keeping them apart.

When two thin lenses are kept in contact we use the above formula for equivalent focal length.

If two thin lenses are held at distance d, then the equivalent focal length is given by

Now let's take problems and solve them using given formulas.

Problems on Compound Lenses.

Let's take the first problem where two converging lenses of equal focal length 50 cm are placed in contact.

Now let's solve for the equivalent focal length for this compound lens.

We use the formula for the lenses in contact for this problem, which is

Therefore, substituting these values in formula we get.

The equivalent focal length for this compound lens is 25 cm.

Taking another problem where two thin lenses of focal length 60 cm and 30 cm are kept at a distance 2 cm apart.

So, let's find out the equivalent focal length for this combination of lenses.

Using the above formula for compound lenses we could solve for the equivalent focal length.

Substituting the above values in the formula we get.

Therefore the equivalent focal length of this compound lens is 0.048 cm.

Revision.

To remove defects from images we use two or more lenses known as Compound lens.

The combination can be made either by keeping the lenses in contact or by keeping them apart.

When two thin lenses are kept in contact we use the above formula for equivalent focal length.

If two thin lenses are held at distance d, then the equivalent focal length is given by

The End.