Concepts Of Physics MCQ Edition [Volume 1]
- Exam
- Concepts Of Physics MCQ Edition [Volume 1]
- Subject
- Physics
- Chapter
- Geometrical Optics
Concepts Of Physics MCQ Edition [Volume 1] · Physics · Geometrical Optics
A converging lens with a focal length of 15 cm and a converging...
A converging lens with a focal length of and a converging mirror with a focal length of are positioned apart, sharing a common principal axis. A point source is situated between the lens and the mirror, at a distance of from the lens. Determine the locations of the two images formed.
Options
- A from the lens towards the mirror, and from the lens away from the mirror
- B from the lens towards the mirror, and from the lens away from the mirror
- C and from the lens, both on the side away from the mirror
- D and from the lens, both on the side away from the mirror
Correct answer
C. and from the lens, both on the side away from the mirror
Step-by-step solution
The light from the point source can form an image in two ways: by directly refracting through the lens, and by first reflecting from the mirror and then refracting through the lens.
For the first image (formed directly by the lens):
The source is at a distance of from the lens.
Using the lens formula :
The positive sign indicates that the image is formed on the side opposite to the object, which is away from the mirror.
For the second image (formed after reflection from the mirror):
The distance between the lens and the mirror is . The source is from the lens, so it is from the mirror.
For the converging (concave) mirror, and .
Using the mirror formula :
The reflected rays become parallel to the principal axis and travel towards the lens.
For the lens, these parallel rays act as an object at infinity ().
Using the lens formula:
Since the rays are coming from the mirror, they pass through the lens and converge on the other side, which is away from the mirror.
Thus, the two images are formed at and from the lens, both on the side away from the mirror.
For the first image (formed directly by the lens):
The source is at a distance of from the lens.
Using the lens formula :
The positive sign indicates that the image is formed on the side opposite to the object, which is away from the mirror.
For the second image (formed after reflection from the mirror):
The distance between the lens and the mirror is . The source is from the lens, so it is from the mirror.
For the converging (concave) mirror, and .
Using the mirror formula :
The reflected rays become parallel to the principal axis and travel towards the lens.
For the lens, these parallel rays act as an object at infinity ().
Using the lens formula:
Since the rays are coming from the mirror, they pass through the lens and converge on the other side, which is away from the mirror.
Thus, the two images are formed at and from the lens, both on the side away from the mirror.