Question
Download Solution PDFAn object is placed at 20 cm in front of a concave mirror and the image formed by this mirror is at 60 cm in front of the concave mirror. What is the focal length of the mirror?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFCONCEPT:
- Concave mirror: The mirror in which the rays converge after falling on it is known as the concave mirror.
- Concave mirrors are also known as a converging mirror.
- The focal length of a concave mirror is negative according to the sign convention.
- Mirror Formula: The following formula is known as the mirror formula:
\(\frac{1}{f}=\frac{1}{u}+\frac{1}{v}\)
where f is focal length v is the distance of the image from the mirror, and u is the distance of the object from the mirror.
CALCULATION:
Given that u = -20 cm and v = -60 cm
Mirror formula \(\frac{1}{f}=\frac{1}{u}+\frac{1}{v}\)
\(\frac{1}{f}=\frac{1}{-20}+\frac{1}{-60}\)
f = -60/4= -15 cm
So the correct answer is option 1.
Last updated on Jul 4, 2025
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