ACTIVITY
A student has focussed the image of a candle flame on a white screen using a
concave mirror. The situation is as given below:
Length of the flame = 1.5cm
Focal length of the mirror = 12cm
Distance of flame from the mirror = 18cm
If the flame is perpendicular to the principal axis of the mirror, then
calculate the following:
1. Distance of the image from the mirror.
(2)
2. Length of the image of the candle by using mirror formula and
similarity criteria.
(1)
3. If the distance between the mirror and the flame is reduced to
10cm, then what would be observed on the screen?
(2)
4. Draw ray diagram to justify your answer for this situation. (2)
5. Define radius of curvature of a concave mirror.
(1)
6. What is the value of linear magnification for a concave mirror
and convex mirror?
Answers
Answer:
Given height of the flame h1=1.5cm
f=-12cm u=18cm
Using the mirror formula
1/f=1/u+1/v
1/v=1/f-1/v
1/v=1/-12 +1/18
1/v =-18+12/18*12
1/v=-1/36
v=-36cm (image distance)
m=-v/u
m=-(-36)/18
m=-2
so the image formed is real inverted and enlarged
height of the image m=h2/h1 (h1-- height of the object h2-- height of the image)
-2=h2/1.5
h2= -3cm
so the image height is 3cm and the negative sign indicates that the image is formed below the principal axis.
Answer:
Explanation:
Given: height of object, h= +1.5cm; focal length,f = -12cm; object distance, z = -18 cm; image distance, v = ?; height of image, h' = ?
Image 1
lf u =- 10 cm, no distinct image would be formed on the screen. In this case the image formed will be virtual.
Image 2
