Light reflection and refraction Worksheet-7

Light reflection and refraction Worksheet-7

 

  1. An object is placed at a large distance in front of a convex mirror of radius of curvature 40 cm. How far is the image behind the mirror ?

 

  1. An object is placed 15 cm from a convex mirror of radius of curvature 90 cm. Calculate position of the image and its magnification.

 

  1. The image formed by a convex mirror of focal length 30 cm is a quarter of the object. What is the distance of the object from the mirror ?

 

  1. When an object is placed at a distance of 60 cm from a convex spherical mirror, the magnification produced is 1/2. Where should the object be placed to get a magnification of 1/3 ? 

 

  1. An object is placed 18 cm in front of a spherical mirror. If the image is formed at 4 cm to the right of the mirror, calculate its focal length. Is the mirror convex or concave ? What is the nature of the image ? What is the radius of curvature of the mirror ?

 

  1. A convex mirror used for rear view on an automobile has a radius  of curvature of 3.00 m. If a bus is located at 5.00 m from this mirror, find the position, nature and magnification of the image.

 

  1. Calculate speed of light in water of refractive index 4/3. Given speed of light in air = 3 × 108 m/s.

 

  1. A ray of light passes from air to glass (n = 1.5) at an angle of 30°. Calculate the anglt of refraction.

 

  1. A ray of light is incident on a glass slab at an angle of 45°. If refractive index of glass be 1.6, what is the angle of refraction ?

 

  1. The refractive index of diamond is 2.47 and that of glass is 1.51. How much faster does light travel in glass than in diamond?

 

Answer:

  1. Here R = 40 cm, u = ∞, v = ?

As      

          v = 20 cm.

 

  1. Here   u = –15 cm, R = 90 cm

          v = ? m = ?

As  

          11.25

          0.75.

 

  1. Here, f = 30 cm, 

As  

As   or

          u = –90 cm.

 

  1. Here, u = –60 cm,

As      

v = 30cm

As   

       

          f = 60 cm

Again 

              

As       

          u’ = –120 cm.

 

  1. Here,  u = –18 cm,     v = 4 cm,   f = ?, R = ?

As    

          5.14 cm

As f is +, therefore, mirror is convex. Image is virtual, erect and smaller in size.

R = 2 f = 2 × 5.14 = 10.28 cm.

 

  1. Here, R = 3.00 m, u = –5.00 m, v = ?, m = ?

         

From      

          1.15 m

The image is virtual, erect and 1.15 m at the back of the mirror

0.23.

 

  1. Here,  

From

          .

 

  1. Here,

From

         

or      r = 19.47°

 

  1. Here, I = 45°, = 1.6; r = ?

From   

Using tables of natural sines, r = 26.2°