# Focal length of convex lens experiment. Determination of the Focal Length of a Convex Lens 2022-10-22

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The focal length of a convex lens is a measure of its ability to focus light. It is the distance from the lens to the point where the light rays converge, or the point at which an object placed at infinity would be in focus. The focal length of a lens is an important parameter in determining its optical properties, as it determines how the lens will behave when used to focus light.

One common experiment used to determine the focal length of a convex lens is the lens equation experiment. In this experiment, the lens is placed between a light source and a screen, and the distance between the lens and the screen is varied until a sharp image of the light source is formed on the screen. The distance between the lens and the screen at which the image is in focus is known as the focal length of the lens.

To perform the experiment, a light source is set up on one side of the lens and a screen is placed on the other side. The distance between the lens and the screen is then adjusted until a sharp image of the light source is formed on the screen. This distance is measured, and the focal length of the lens is calculated using the lens equation:

1/f = 1/d1 + 1/d2

where f is the focal length of the lens, d1 is the distance between the lens and the light source, and d2 is the distance between the lens and the screen.

The lens equation experiment is a simple and effective way to determine the focal length of a convex lens. It can be performed with a variety of different lenses, including those made of glass, plastic, or other materials. The experiment can also be used to compare the focal lengths of different lenses, or to determine the effect of changing the shape or material of a lens on its focal length.

In conclusion, the focal length of a convex lens is an important parameter that determines how the lens will behave when used to focus light. The lens equation experiment is a simple and effective way to determine the focal length of a lens, and can be used to compare the focal lengths of different lenses or to study the effect of changes in the shape or material of a lens on its focal length.

## CBSE Class 10 Science Lab Manual A convex lens of less than 20 cm focal length 6. Answer: Pole is the mid-point of the mirror which makes the incident light to go at some angle on the other side of principal axis. Experiment: Determination of the Focal Length and The power of a lens is determined by its ability to create a difference of light. Focal Length of Concave Lens Experiment Experiment: Determine the focal length of a concave lens by combining it with a suitable convex lens. What will be the nature of the image formed by a concave mirror for a distant object? Fix it in the outer, laterally movable upright close to zero ends. Answer: A convex mirror is an opaque optical tool.

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## Convex Lens Simulation In part A, I experimented using a single lens at a time, while in part B, I used 2 lens in contact at a time. In a concave mirror, rays of light are parallel to its principal axis and meet at a single point on the principal axis, after reflection from the mirror as shown in Fig. The distance from the lens to that point is the principal focal length f of the lens. Where f is the focal length, u is the distance between the object and the lens v is the distance between the image and the lens. The image will be virtual for the object between the pole and the focus. Repeat the experiment for four or five different values of u.

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## Experiment: Determination of the Focal Length and Power of a Lens So I pulled down the blinds of the windows and also made sure that there was no draught present in the room that can make the candle flame unstable. The distance between the center of the convex lens and its principal focus is called its focal length. As, the focal length of a convex lens is equal to the distance between optical centre and any of its focus. This point is one of the two foci of the lens. What type of mirror is used as a shaving mirror or in vanity boxes? Is a convex mirror a transparent or opaque optical tool? If the lens is bent outwards, the lens is known as a convex lens.

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## Focal Length of Concave Lens Experiment To determine the focal length of a concave mirror, a student focuses a classroom window, a distant tree and the Sun on the screen with the help of a concave mirror. Real and Virtual Images: Lenses produce images by refraction that are said to be either real or virtual. Answer: The light from the Sun is converged at a point, as the sharp, bright spot by the mirror. Turn the face of mirror towards a distant object suppose a tree. Adjust the distance of screen, so that the image of the distant object is formed on it as given in the figure below. Three uprights with clamps 5. Note down the position of the index mark on the foot of the upright of the lens, the image needle, and the object needle in the second observation column.

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## Determination of the Focal Length of a Convex Lens How can we find the focal length of a concave mirror, when the image is obtained by using a concave mirror? That means a power of that lens is more. For diverging or convex mirrors, the focal length is always positive. Is silvering in mirrors generated by applying a silver coating or some other substances? Adjust the object needle upright, and place it at a distance close to 1. . In which case, will the student is closer to accurate value of focal length? How will you distinguish between a convex and concave lens? It diverges light rays away from principal axis. It brings the rays of light passing through it closer together i. Can we use convex mirror to find its focal length experimentally Why? This sphere has a centre.

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## To Find Focal Length of a Convex Mirror Using a Convex Mirror Answer: It depends upon the focal length of the lens. Answer: Biconvex lens is the lens found in the human eye. Next, find the distance between the tip of the image needle and the optical centre of the lens, as mentioned. You are provided with two convex lenses of same aperture and different thickness. If the lens used in the experiment is a plano-convex lens, then what is the radius of curvature of the plane surface? Reflection by Convex Lens When the parallel beam of light coming from a distant object such as the sun, a building, a tree, etc. Image formed may be real or virtual. The image of the sun should never be seen directly with the naked eye or it should never be focussed with a convex lens on any part of the body, paper or any inflammable material as it can burn.

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## Determination of the Focal Length of a Convex Lens Consequently, I adjusted the length of v until a sharp and focused image was seen. Sunlight should never be focused on any part of the body as it can burn it. Give the condition to hold a mirror for finding the focal length of the concave mirror. What is law of reflection for a mirror? How will you distinguish between a concave and a convex mirror? In such a position sunlight would be parallel to the optical axis of the lens. Can this method be used to find the approximate focal length of the concave lens? Answer: It bends away from the normal at the point of incidence on the interface. In which case will the student get more accurate value of focal length? Reflection by Concave Mirror A concave mirror obeys the laws of reflection of light. What is the focal length of convex mirror lens? Fix the convex lens in the holder.

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## To find the focal length of a convex lens by plotting graphs between u and v or between 1/u and 1/v. In part A, I experimented using a single lens at a time, while in part B, I used 2 lens in contact at a time. A convex lens is a piece of round glass that is thicker at the centre than at the edges. Answer: The reason behind the blurred image is that the mirror is away from the object. The straight line will intersect the axes at equal distance from the origin. Where f is the focal length, u is the distance between the object and the lens v is the distance between the image and the lens.

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## How do you find the focal length of a convex lens experiment? Answer: Yes, it forms virtual image only when placed between focus and optical centre and for all other positions, it forms real image. Index needle or a knitting needle 4. How To Set Up 1. Adjust the object needle upright towards the mirror in steps 1cm to obtain observations 1 and 2. State the importance of pole of a mirror. Repeat this measurement five times. Repeat procedures 3 to 5 to note down at least five various locations of the lens and the object.

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