Physics Practicals Class 12

Concave Mirror – Refractive Index of Water

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About Simulation

  • Refractive index of water using concave mirror experiment is one of the important class 12 physics practicals that you can learn in our virtual lab.
  • This simulation will give an entire idea about the image formation by concave mirror and the refractive index of water using a concave mirror.
  • In this simulation, you will learn the concept of reflection of light, image formation using a concave mirror, and the difference between concave and convex mirror.
  • You will get the knowledge of determining focal length, basics of concave mirror, and refractive indices.
  • You will be able to do the experiment in a real-lab-like setup by understanding the procedure.

Concave Mirror Refractive Index of Water

  • All the experiment steps and procedures like measuring the focal length of a mirror, noting down the readings using a spirit level, 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


Concave mirrors form both real and virtual images. When the concave mirror is placed very close to the object, a virtual and magnified image is obtained and if we increase the distance between the object and the mirror, the size of the image reduces and real images are formed.

The figure below describes the image formation of an object using a concave mirror. Here figure (a) shows the concave mirror without water and figure (b) shows the concave mirror filled with water.

In the figure, MM′- is the reflecting surface of a concave mirror

  • P – pole of the mirror
  • C – centre of curvature
  • 𝑢 – object distance
  • 𝑣 – image distance
  • R – radius of curvature
  • 𝑖 – angle of incidence
  • 𝑟 – angle of refraction

When an object is placed in front of MM′ at a distance equal to R, a real and inverted image is formed at centre of curvature.

𝑢 = 𝑣 = R = distance PC

The centre of curvature is located by the method of parallax between a sharp-edged pin and an image formed by the concave mirror.

C′ is the center of curvature when the mirror is partially filled with water. The parallax between the object pin and the image pin is removed at a shorter distance from the pole. The incident ray is refracted at the water-air boundary. The reflected ray retraces back on the same path.

Fig. (b) shows the refraction in water.
Let, ZZ′ be the normal, ∠ZNC′ and ∠ZNC be the angle of incidence and angle of refraction, respectively.

Using geometry,

∠𝑖 = ∠NC′P and ∠𝑟 = ∠NCP

According to Snell’s law,

$$n_{w a}=\frac{\sin i}{\sin r}=\frac{\mathrm{NC}}{\mathrm{NC}^{\prime}}$$

For mirrors with small aperture and large radius of curvature,

NC ≈ PC,NC′ ≈ PC′

$$\Rightarrow n_{w a}=\frac{\mathrm{PC}}{\mathrm{PC}^{\prime}}=\frac{\mathrm{R}}{\mathrm{R}^{\prime}}$$

Using this formula, we can determine the refractive index of any liquid.

Requirements for this Science Experiment

Concave Mirror Plumb Line Water Optical Needle Clamp Stand Dropper

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