Combination of a lens and a mirror

In most optical instruments, two or more lenses are employed in sequence. The lens formula or ray diagram can be used to determine the final image’s location, size, and nature. In any instance, the picture created by the first lens is located first. The final image created by the second lens can be located by using that image as the object for the second lens. An object’s image can be rendered erect and greatly amplified if more than two lenses are present. As a result, a proper combination of lenses is utilized in high-powered optical equipment. This is why the combination of a mirror and lens is used in a microscope. Let us study the process in detail and from the basics.

State Refraction

When a beam of light collides with another transparent medium, some of it is reflected into the original medium while the rest passes through. Let us represent a beam by a ray of light. 

At the interface of the two media, an obliquely incident ray of light that enters the other medium alters. The refraction of light is the term for this phenomenon. Willebrord Snell discovered the following refraction rules through experimentation:

(I) Experimentally, at the point of incidence, the incident ray, the refracted ray, and the normal to the interface all will lie on the same plane.

(ii) It was noticed that the sine of the angle of incidence is proportional to the sine of the angle of refraction.

Remember that the angles of incidence I and refraction (r) are formed by the incident and refracted rays with respect to the normal.

We have (sin i/sin r)= n21, where n21 is a constant referred to as the second media’s refractive index in relation to the first medium. We should remark that n21 is a property of the pair of media (and is also affected by light wavelength), but it is unaffected by the angle of incidence.

If n21 > 1 the refracted ray bends towards the normal. Medium 2 is optically denser (or denser, in short) than medium 1 in this scenario. If n21 >1, r > i, on the other hand, the refracted beam bends away from the normal. When an incident ray in a denser medium refracts into a rarer medium, this is the case.

State Total Internal Reflection

This is the phenomenon where light is partly reflected into the same medium when it goes from an optically denser medium to a rarer medium at the interface.

The second medium was partially refracted. Internal reflection is the name given to this type of reflection. With a magnifying glass, visual phenomena can be easily shown.

Nowadays, a laser torch or pointer is readily available. Next, take a beaker and fill it with clean water. Using a piece of soap, stir the water a few times, causing it to become slightly obscure. Take a laser pointer and shine it around the room. The light shines through the opaque water. You’ll notice that the beam’s route isn’t straight. The water inside gleams beautifully. Total internal reflection produces brighter images than mirrors or lenses, or a combination of a lens and a mirror because 100 percent of incident light is reflected into the same medium without any loss of intensity. In contrast, reflection from mirrors and lenses always results in some loss of intensity.

State the combination of thin lenses

Consider a combination of thin lenses in contact, A and B, with focal lengths of f1 and f2, respectively, in contact.

On the common primary axis, an object is placed at O. The first lens A creates an image at I1, which serves as the subject for the second lens B. At I, the final image is created.

Let a point object O be placed at a distance p from the lens L1 whose real image is formed at a distance q1. From the lens formula,

I/p + 1/q1 = 1/f1 ……(1)

Where f1 signifies the focal length of lens L1.

This image now serves as a virtual object for the second lens L2 of focal length f2 if we neglect the small separation between the lenses. The distance of this virtual object from lens L2 will be the same as its distance from the lens L1, i.e.

-1/q1 + 1/q = 1/f2……..(2)

Adding equation(1) and (2) we get,

1/p + 1/q1 – 1/q1 + 1/q = 1/f1 + 1/f2

Or,

1/p + 1/q = 1/f1 + 1/f2

Now, suppose we replace the combination of thin lenses of focal lengths f1 and f2 with the single lens of focal length f such that it forms an image at a distance q of an object placed at p from it. In that case, such a lens is called an equivalent lens, and its focal length is known as equivalent focal length.

State the combination of lenses and mirrors

The most obvious difference between mirrors and lenses is that mirrors reflect light beams (light bounces back), whereas light rays are refracted (pass-through) a viewpoint. A mirror will only have one point of convergence, which will be directly in front of the mirror. On either side of a lens, there are two central focuses.

The similarity between a concave mirror and a convex lens is that light converges at the point of convergence in both a concave mirror and a raised lens. However, at the point of convergence, the elevated mirror and inward lens effectively divide the light.

When we combine several lenses or mirrors in a co-axial direction, the image formed by the lens serves as the object for the next lens or mirror, and the image formed by this setting will serve as the image for the third lens. The total magnification we get for the combination of a lens and a mirror is :

M = m1*m2*m3*……..

Conclusion

In optics and technology, refraction has numerous applications. The following are a handful of the most well-known applications: For many purposes, such as magnification, a lens employs refraction to generate an image of an object.

The theory of refraction is used in spectacles worn by those with poor vision.

Peepholes in home doors, cameras, movie projectors, and telescopes utilize refraction. In addition, optical characteristics are used in various domains of physics. For example, in the case of lenses (both convex and concave), the refraction phenomena are used to create a picture of the object.

Geometrical optics is a branch that explores how pictures form in optical systems. It is used in the optical diagnosis of the secrets of the human body in medical applications. It is also employed in the treatment and surgical procedures of human tissues.