Light reflection and refraction Worksheet-6

Light reflection and refraction Worksheet-6

1. Focal length of a convex mirror is 50 cm. What is its radius of curvature ?

2. Radius of a concave mirror is 25 cm. What is the magnification produced ?

3. A concave mirror produces 10 cm long image of an object 2 cm. What is the magnification produced ?

4. An object 1 cm high is held near a concave mirror of  magnification 10. How tall will be the image ?

5. Find the size, nature and position of image. Formed by a concave mirror, when an object of size 1 cm is placed at a distance of 15 cm. Given focal length of mirror is 10 cm.

6. An object 2 cm high is placed at a distance of 16 cm from a concave mirror, which produces 3 cm high inverted image. What is the focal length of the mirror ? Also, find the position of the image.

7. An erect image 3 times the size of the object is obtained with a concave mirror of radius of curvature 36 cm. What is the position of the object?

8. A 2.5 cm candle is placed 12 cm away from a convex mirror of focal length 30 cm. Give the location of the image and the magnification.

9. An object is placed in front of a concave mirror of focal length 20 cm. The image formed is three times the size of the object. Calculate two possible distances of the object from the mirror ?

10. A concave mirror produces a real image 10 mm tall, of an object 2.5 mm tall placed at 5 cm from the mirror. Calculate focal length of the mirror and the position of the image ?

Answer:

1. Here, f = cm, R = ?

From R = 2 f = 2 × 50 = 100 cm.

2. Here, R = 25 cm, f = ?

From f =12.5 cm.

4. Here, h₁ = 1 cm, h₂ = ? m = ± 10

From m =

.

As

∴

ν = –30 cm

Negative sign of ν shows that the image is real.

As     

h₂ = –2 cm

Negative sign of h₂ shows that the image is real and inverted. 

6. Here,

h₁ = 2cm, u = –16cm, h₁ = –3cm

f = ? v = ?

As                

v = –24 cm.

As           

       = –9.6cm.

7. Here, m = 3, R = –36 cm, u = ?

As  m = 3 = or v = –3 u

As     

          3 u = –36, u = –12

8. Here, h₁ = 2.5 cm,  u = –12 cm

          f = 30 cm, v = ?, m = ?

As        

          = = 8.6 cm.

Positive sing of v shows that the image is virtual.

                     or       

          h₂ = 1.7 cm

9.  –40/3 or –80/3 cm

m = ±3.

10. Here  h₂ = –10mm, h₁ = 2.5 mm

          u = –5cm, f = ?, v = ?

As                 or    v = –20 cm

Negative sign of shows that image is real.

–4 cm.