Physics Practicals Class 12

Convex Lens and Plane Mirror – Refractive Index of Water

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About Simulation

  • Refractive index of water using convex lens and plane mirror experiment is one of the important class 12 physics practicals that you can learn in our virtual lab.
  • In this simulation, you will learn the concept of refraction of light, image formation using an equiconvex lens backed by a plane mirror, and the difference between real and virtual images.
  • You will get the knowledge of determining focal length, the basics of a convex lens, and refractive indices.
  • This interaction provides a very immersive environment and gives you a real-lab-like experience while conducting or performing experiments.

Convex Lens and Plane Mirror – Refractive Index of Water

  • All the experiment steps and procedures like measuring the focal length of a combination of lenses, noting down the readings using a meter scale, plumb line, etc., and many more are highly interactive and have been simulated in a very similar manner as you do in a physics lab.
  • This will help learners to better prepare for various competitive exams such as IIT-JEE (JEE Main & Advanced), NEET, and Olympiads.

Simulation Details

Duration – 30 Minutes
Easily Accessible
Language – English
Platforms – Android & Windows


Plane mirrors form virtual, laterally inverted, and erect images. The size of the image is the same as the size of the object. The distance between the image obtained from the mirror is the same as the distance between the object from the mirror.

Concave Mirror Refractive Index of Water

Above figure describes the formation of an image using an equiconvex lens backed by a plane mirror. Here figure (a) shows image formation when there is air between the lens and a mirror and figure (b) shows image formation when water is placed between the lens and a mirror.

The focal length of water lens (𝑓𝑤) can be determined as, $$\frac{1}{f^{\prime}}=\frac{1}{f}+\frac{1}{f_w}$$

Where, 𝑓′ is the focal length of combination of two lenses

𝑓 is the focal length of convex lens $$\Rightarrow \frac{1}{f_w}=\frac{f-f^{\prime}}{f f^{\prime}}$$

According to the sign convention, $$f=+v e, f^{\prime}=+v e, f_w=-ve$$

$$\Rightarrow f_w=\frac{f f^{\prime}}{f-f^{\prime}}$$

Using Len’s maker formula for the plano-concave lens,

$$\frac{1}{f_w}=\left(n_{w a}-1\right) \frac{1}{R}$$

Where, 𝑅 is the radius of curvature

𝑛𝑤𝑎 is the refractive index of water with respect to air

$$\Rightarrow R=\left(n_{w a}-1\right)\left(\frac{f f^{\prime}}{f-f^{\prime}}\right)$$

$$\Rightarrow n_{w a}=\left(1+\frac{R}{f_w}\right)$$

Hence, the refractive index of any liquid can be determined.

Requirements for this Science Experiment

Convex Lens Plane Mirror Plumb Line Water Optical Needles Clamp Stand Dropper

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