Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
33.7k views
in Physics by (45.7k points)

A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is 

(a) – 30 cm 

(b) – 20 cm 

(c) – 40 cm 

(d) – 60 cm

1 Answer

+1 vote
by (46.2k points)
selected by
 
Best answer

The answer is (b) – 20 cm

Here, size of object = O = + 10.0 mm = + 1.0 cm (as, 1 cm = 10 mm) 

Size of Image size = I = 5.0 mm = 0.5 cm 

Image distance, v = − 30 cm (as image is real) 

Let, object distance = u 

Focal length, f =? 

Magnification m= I(Size of image) /O(Size of image)

U= -60cm

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...