Name: _____________________________
Activity 2.5
Images Formed in Curved Mirrors
Purpose
1. To demonstrate how an image is formed
2. To demonstrate how real image differs from virtual image
Materials
Optical bench apparatus
Curved mirror (concave mirror),
Flashlight,
black paper
Procedure
1. Cut an arrow shape out of a black paper and tape it at the flat surface of a flashlight. The
flashlight act as the source of light while the arrow acts as the object.
2. Position the mirror intact with the mirror stand at the center of two metersticks as shown
below.
screen
mirror
light
source
Experimental Setup.
3. Mark the optical bench metersticks at the following points:
 The focal point F
 At the center of curvature C which is equal to 2F
4. Allow the light rays coming from the flashlight to strike the mirror.
5. Place the flashlight at a distance farther than the focal point of the mirror.
6. Place a screen (a white cardboard) at a distance in front of the mirror. Move the screen at
different distances in front of the mirror until a clear and sharp image is formed. Let
students record the location, position, and size of the image. Do the same thing at
different location of the flashlight.
7. Place a summary of your recorded observations on a table similar to the data table below.
Data Table
Location of Object
Location of
Image
Kind of image
(real or virtual)
Position of
image (erect or
inverted)
Size of Image
(reduced or
enlarged)
A. CONCAVE
At infinity
Farther than the Center of
Curvature
At the center of
Curvature
Between the Center of
curvature and the Focal
point
At the focal point
Between the focal point
and the center of the lens
B. CONVEX
All locations
Guide Questions
1. Describe the image changes in size and location as the object approaches the mirror.
2. Differentiate a real image from a virtual image.
3. Describe the images formed by curved mirrors (convex and concave mirrors).
Activity 2.0
Focal length of the lens
Purpose
To determine the focal length of the convex lens
Materials
Convex lens
Optical Bench
Procedure
1. Look for any object (tree, etc.) outside your window.
2. Hold up the lens facing the window.
3. Move a sheet of paper (screen) behind it. See figure on the right.
4. Adjust the paper until a clear image of the distant object (tree, etc.) outside the
window is observed on the paper.
5. Measure the distance from the image to the lens. This is the focal length of the lens.
Guide Question:
1. What is the focal length of your lens?
2. If you take an object that is farther than the first one, do you think you will have the
same measurement? Find it out by considering another object.
Activity 2.1
Image Formed in lenses
Purpose
To locate and describe the image formed by concave and convex lenses
Materials
Concave les
Convex lens
Flashlight / Candle
Optical Bench
Candle
Screen
Lens
Procedure
1. Start with a convex lens. Get its focal length
2. Position the candle on the following: (these are the
object distances)
1.1 before the focal length of the lens (between 1F and the lens),
1.2 at the focal length F,
1.3 between F and 2F,
1.4 at 2F, and
1.5 beyond 2F
3. In all cases adjust the screen until a clear image is seen.
4. Measure the distance from the image to the lens. This is the image distance.
Describe also the nature of the image and enter in the data table.
5. Repeat steps 1-4 using a concave lens.
Table 2.11
Location of Object
(object distance)
A. CONVEX
between 1F and the lens
at the focal length F
between F and 2F
at 2F
beyond 2F
B. CONCAVE
between 1F and the lens
Location of Image
(image distance)
Kind of
image
Position of
image
at the focal length F
between F and 2F
at 2F
beyond 2F
Guide Question
1. Compare the nature of the image at different object distances for
1.1 Convex lens
1.2 Concave lens
Size of
Image