Question 3 - Case Based Questions (MCQ) - Chapter 10 Class 10 - Light - Reflection and Refraction

A student wants to project the image of a candle  flame on a screen 60 cm in front of a mirror by  keeping the flame at a distance of 15 cm from its  pole.  

(a) Suggest the type of mirror he should use:  

(i) convex mirror 

(ii) plane mirror  

(iii) concave mirror 

(iv) none of the above  

Ans. 

Since the student wants image on a screen , it has to be a real image

Now, let’s check both mirrors

• Convex mirrors always produce virtual images . It cannot be used to produce images on the screen.
• Concave mirrors produce real images on the screen in all cases except when the object is between pole and focus , therefore students should use a concave mirror because it forms real images.
• Plane mirrors always form virtual images. So, it cannot be used

So, the correct answer is (iii) Concave mirror  

(b) Find the linear magnification of the image  produced.  

(i) – 4 

(ii) + 4  

(iii) – 900 

(iv) + 900  

Ans. 

So, the correct answer is (i) – 4 

(c) When object distance is less than focal length the image is _______ and when object distance is more  than focal length the image is  ______.  

(i) real, real 

(ii) virtual. Virtual  

(iii) real, virtual 

(iv) virtual, real

Ans. 

In a concave mirror

• When object is kept between Focus and Pole , image formed is virtual
• When object is kept beyond focus (between C and F, at C and beyond C), image formed is real 

So, the correct answer is (iv) virtual, real 

(d) Draw  a ray diagram for the given scenario. 

Answer

(e) What is the distance between the object and its image?  

(i) 15 cm 

(ii) 45 cm  

(iii) 75 cm 

(iv) 0 cm  

Ans.

Given

Object distance, u = -15cm

Image distance, v = -60cm

Now,

Distance between object and image = u - v 

= -15 - (-60)

= 45cm

The correct answer is (ii) 15 cm 

(e) The image formed in the above case is:  

(i) virtual, inverted and magnified.  

(ii) real, erect and magnified  

(iii) real, inverted and magnified  

(iv) real, erect and diminished  

Ans.    

• Since the image is formed on a screen , it is real .

Also, we calculated the magnification of the image as m= -4. 

• Since M = image size/object size, it is clear that the image is 4 times larger than the object. 
• Hence it is magnified. 
• The negative sign in the magnification means that the image is inverted.  

Thus, the correct answer is (i) real, inverted and magnified