Following figure illustrates the ray diagram for the formation of images by a concave mirror. The position of the object is beyond the centre of curvature of the concave mirror. On the basis of the given diagram, answer any four questions from (a) to (e).
(a) If the focal length of the concave mirror is 10 cm, the image formed will be at a distance ___________.
(i) Between 10cm and 15cm
(ii) Between 10cm and 20cm
(iii) Beyond 20cm
(iv) At 20 cm
- As seen from the figure, the image formed is between focus and centre of curvature
- Thus, Image is formed between 10 and 20 cm.
So, the correct answer is (ii)
(b) In case of a concave mirror, the image distance is _________ when image is formed in front of the mirror and _________________ when the image is formed behind the mirror.
(i) positive, negative
(ii) negative, negative
(iii) negative, positive
(iv) positive, positive
According to the sign convention for concave mirror
- The image distance is negative when the image is formed in front of the mirror
- The image distance is positive when the image is formed behind the mirror .
So, the correct answer is (iii) - negative, positive
(c) If the size of the object in the given figure is 5 cm and the magnification produced is –0.5. The size of the image is (in cm) ___________
So, the correct answer is (i) – 2.5
(d) A negative sign in the magnification value indicate that the image is ____________
(i) Real and inverted
(ii) Real and erect
(iii) Virtual and erect
(iv) Virtual and inverted
So, the correct answer is (i) Real and inverted
(e) An image formed by concave mirror is virtual, when the object is placed:
(i) at infinity
(ii) at C
(iii) Between C and F
(iv) Between P and F
From figure we note that:
- If we place Object between P ole and F ocus
- Concave mirror forms virtual and erect images.
So, the correct answer is (iv) = Between P and F