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Determination of Focal Length of Concave Mirror and Convex Lens
Before getting started with the experiment, it is important to understand a few terms that are used in a concave mirror and convex lens:
- Centre of curvature: For a curved mirror, the centre of curvature, C can be defined as the centre of a hollow glass sphere of which a curved mirror is a part.
- Radius of curvature: For a curved mirror, the radius of curvature, R can be defined as the radius of the hollow glass sphere of a spherical mirror is part.
- Principal axis: Principal axis is defined as the imaginary line passing through the pole and centre of curvature of the spherical mirror.
- Principal focus: Principal focus is defined as a point at which the reflected rays meet or appear to meet for the spherical mirror. For a concave mirror, the principal focus is in the front and for a convex mirror, the principal focus is at the behind.
Below is an experiment to determine the focal length of a concave mirror and convex lens.
Read More: Convex Lens
To determine the focal length of:
- Concave mirror
- Convex lens by obtaining the image of a distant object.
How to Find Focal Length of Concave Mirror?
Following are the ways to obtain the focal length of the concave mirror:
- A concave mirror is defined as the spherical mirror whose reflecting surface is curved inwards and follows laws of reflection of light.
- The light rays coming from a distant object can be considered to be parallel to each other.
- If the image formed is real, inverted and very small in size, then the parallel rays of light meet the point in the front of the mirror.
- The image formed by the convex lens is real and can be obtained on the screen.
- f is used to denote the difference between the principal axis P and the focus F of the concave mirror.
How to Find the Focal Length of Convex Lens?
Following are the ways to obtain the focal length of convex lens:
- The convex lens is thicker in the middle and thinner at the edges and is also known as the converging lens.
- The refracted rays from the parallel beam of light converge on the other side of the convex lens.
- If the image is obtained at the focus of the lens, the image would be real, inverted and very small.
- f is the focal length which is the difference between the optical centre of the lens and the principal focus.
- The image can be obtained on the screen as the image formed by the lens is real.
To Determine Focal Length of a Given Concave Mirror
Materials required.
- A concave mirror
- A measuring scale
- A screen holder
- A mirror holder
- A mirror stand
- The distance between the selected distinct object should be more than 50 ft.
- The concave mirror placed on the mirror stand and the distant object should be facing each other.
- The screen should be placed in front of the reflecting surface of the mirror. To obtain a clear, sharp image the screen should be adjusted.
- Using a metre scale the distance between the concave mirror and screen can be determined. The distance is the same as the focal length of the given concave mirror.
- Repeat the above procedure thrice to calculate the average focal length.
Experimental Setup
Observation Table
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| 1 | 60 cm | 50 cm | 10 cm |
| 2 | 60 cm | 50 cm | 10 cm |
| 3 | 60 cm | 50 cm | 10 cm |
Calculation
Following is the mean value of the focal length of concave mirror:
10 cm is the focal length of the concave mirror.
Precautions
- To get a well illuminated and distinct image of the distinct object, the distant object should be well illuminated.
- A concave mirror should be always placed near an open window.
- The polished surface of the concave mirror and the distinct object should be facing each other.
- There should not be any hurdle between the rays of light from the object and the concave mirror.
- The screen and the concave mirror stand should be parallel to the measuring scale.
- The mirror holder along with the mirror should be perpendicular to the measuring scale.
To determine focal length of a convex lens
- A wooden bench
- A convex lens
- A lens holder
- A screen fixed to a stand
- Without disturbing the lens and screen, arrange both of them on the wooden bench.
- Place the lens on the holder facing a distant object.
- Place the holder with the screen on the bench.
- The position of the screen should be such that the sharp image of the distant object is obtained on it.
- The difference between the position of the lens and the screen is equal to the focal length of the given convex lens.
- Now shift the focus to towards various other distant object and calculate the focal length of the convex lens.
| 1 | 60 cm | 50 cm | f = 10cm |
| 2 | 60 cm | 50 cm | f = 10cm |
| 3 | 60 cm | 50 cm | f = 10cm |
Following is the mean value of the focal length of convex lens:
10 cm is the focal length of the convex lens.
- The placing of the convex lens should be vertical.
- There should not be any hurdle between the rays of light from the object and the convex lens.
- The convex lens stand and the screen should be parallel to the measuring scale.
Viva Questions
Q1. Differentiate between convex lens and concave lens. Ans: Following is the table explaining the difference between the convex lens and the concave lens:
| The focal length is positive | The focal length is negative |
| Image obtained can be either real or virtual | Image obtained is always virtual |
| The light rays are converged towards the principal axis | The light rays diverge away from the principal axis |
Q2. Name two types of spherical mirrors Ans: Following are the two types of spherical mirror:
- Convex mirror
Q3. What is the relationship between focal length T and the radius of curvature R of a concave mirror? Ans: Following is the relationship between focal length and the radius of curvature:
Q4. What is the mirror formula? Ans: Following is the mirror formula:
Q5. What is law of reflection for a mirror? Ans: Following is the law of reflection for a mirror:
- The incident ray, the reflected ray and the normal all lie in the same plane.
- The angle of incidence is equal to the angle of reflection.
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USEFUL INFO THANK YOU
It is very helpful
If they ask that what theorem we have used in this experiment of the convex lens, can we write that rays from a distant object converge at the focal plane?
Very helpful
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Foundation PHY094 lab report convex lens. Course. Foundation Study of Physics (PHY094) ... Convex Lens Experiment. GROUP MEMBERS : MUHAMMAD FAZRI BIN JASMIN 2020861306. ... INTRODUCTION. A lens is a transparent piece of glass or plastic with at least one curved surface that is used to.
side for. converging lenses and emerges from the lens on the opposite side, parallel to the optical axis. For diverging lenses, one draws Ray 3 starting from the top of the object and projects it to the focal point on the far. side of the lens.
Focal Length of Convex LensB11 Lab Report Objectives of the experiment: To determine the focal length of a spherical convex lens ♦ by "Lens formula method" ♦ by "Lens replacement method". To compare both methods. Theory: In this experiment, we have chosen two methods to find out the focal length of a spherical lens.
PROCEDURE. 1. Finding the focal length of a convex lens. Put the lens at the center of the meter stick. Place the screen and screen support at the 75 cm mark on the meter stick. Take the meter stick out of the supports and bring it to the window. Aim the meter stick at a distant object that can be seen through the window (fig 1).
1. The Focal Length and Magnification of a Converging, Convex Lens (Lab Report) Procedure: 1) Attach the light source to one end of the optics. track as shown in Figure 2. Carefully place the convex lens in the lens mount and verify. that the lens is as close to centered in the lens.
two or more lenses. Convex or converging lenses have positive (+) focal lengths while concave or diverging lenses have negative (-) focal lengths. Virtual Images: If an object distance is less than the focal length of a convex (converging) lens, the light rays on the image side of the lens will diverge. You will see no real image on a screen.
Thin Lenses Name: Lab Partner: Section: 10.1 Purpose In this experiment, the formation of images by concave and convex lenses will be explored. The application of the thin lens equation and the magnification equations to single and compound lens systems will be investigated. 10.2 Introduction 10.2.1 The Thin-Lens Equation
Put a small piece of paper. The ray diagram for finding the on one of the pins (say on image pin P′) to focal length of a convex lens. differentiate it from the object pin P′. 6. Displace the object pin P (on left side of the lens) to a distance slightly less than 2f from the optical centre O of the lens (Fig. E 10.3).
Convex lenses are those that bulge outward in the center, with the edge being the narrowest part. Because light passing through such lenses converges to a point on the other side as described above, these are known as converging lenses. Definition: Convex and Concave Lens. A convex lens is a lens that possesses at least one surface that curves ...
and convex (diverging) mirrors as well as converging (biconvex) and diverging (biconcave) lenses and the different ways they bend light from an object. The objectives of this experiment are as follows: 1. To study the imaging properties of mirrors and lenses. 2. To measure the image distances and heights produced by various mirrors and lenses. 3.
The lateral magnification of the lens (the size of the image relative to the object) is given by: =. − p. If the image is real (i > 0), as in the figure, the resulting magnification is negative, meaning that the image is inverted with respect to the object. You will be provided a high intensity lamp source, a white screen, an optical rail, a ...
2. Starting with the lens close to the screen, slide the lens away from the screen to a position where a clear image of the crossed-arrow object is formed on the screen. Measure the image distance and the object distance. Record these measurements (and all measurements from the following steps) in Table 2 of your student report. 3.
Lab report for determining the focal length of a convex lens lab report phy260 universiti teknologi mara, sabah kota kinabalu campus geometrical optics (phy260 ... DETERMINING THE FOCAL LENGTH OF A CONVEX LENS DATE OF EXPERIMENT: 23 APRIL 2020 DATE OF SUBMISSION: 5 MAY 2020 LECTURER: MR MOHD RUZALEH NURDIK. Format 1. Method 1. Data 2. Analysis ...
This report presents a lab experiment that hopes to introduce and familiarise students with the concept of light and lenses. Lenses have been studied for over 2000 years and, today they have many ...
1) 5. Hold lenses carefully by the edge. Project the image of a distant object on a screen. One way to achieve this is to take the lens and a ruler to a long hall-way. Hold the lens such that light from a distant light source at the other end of the hallway passes through the lens and focuses on the wall. 6.
2. Find image distance (i1). Record. 3. Place second lens (f=-9) at 4cm from light. 4. Move screen until a clear image is obtained. Record image distance (i 2). 5. Repeat procedure by adding 21 cm lens at 40cm from light. During the course of this experiment, I assisted my lab partners in setting up this experiment.
Objective: The objective of this experiment is to measure the focal length of a converging lens and a diverging lens. Theory: Light refracts when passing through media with different indices of refraction. This property can be utilized to bend light in useful ways. converging (convex, positive) lens can be used to focus parallel light rays and ...
A. Choose a converging lens for the experiment. By definition, the focal length . f. of a lens is the image distance from the lens center, for an infinitely distant object. To obtain a rough estimate of . f, project an image of some distant object, e.g. a tree, in the space outside the lab onto the white paper. Q1. Why does the object appear ...
Part 1 - Conduct an experiment to verify the thin lens equation for a convex (converging lens). You need to create a data table in your lab notebook, deciding on number of columns to be included in the table. Record all the data you take, even though some data may not be within the expected value. This is an experiment and hence uncertainty ...
Introduction. xperiment O17a. Thin Lenses. Introduction:Lenses are crucial parts of many optical instruments, starting from a simple magn. fying glass, to modern optical telescopes. They also play an important role in everyday life such as the correc. n of nearsightedness and farsightedness. When a ray of light passes through a lens, it changes ...
Principal focus: Principal focus is defined as a point at which the reflected rays meet or appear to meet for the spherical mirror. For a concave mirror, the principal focus is in the front and for a convex mirror, the principal focus is at the behind. Below is an experiment to determine the focal length of a concave mirror and convex lens.
The objectives of this experiment are to determine the focal length of a convex lens by plotting a graph of versus and to determine the magnification of a convex lens. PROCEDURE Due to the pandemic of Covid-19, this face-to-face lab session that was supposed to be a hands on experiment has been canceled.