A concave lens has a focal length of −2 cm. What is its power?

This question was previously asked in
RRB JE CE 22 Apr 2025 Shift 1 CBT 2 Official Paper
View all RRB JE Papers >
  1. 25 D
  2. −50 D
  3. −0.5 D
  4. 0.5 D

Answer (Detailed Solution Below)

Option 2 : −50 D
Free
General Science for All Railway Exams Mock Test
2.1 Lakh Users
20 Questions 20 Marks 15 Mins

Detailed Solution

Download Solution PDF

The correct answer is -50 D.

Key Points

  • A concave lens is a lens that diverges light rays that are incident upon it.
  • The focal length of a concave lens is always taken as negative because it diverges light rays.
  • The formula to calculate the power of a lens is P = 1/f, where P is power in diopters (D) and f is the focal length in meters.
  • Given the focal length f = -2 cm, we need to convert it to meters: -2 cm = -0.02 m.
  • Using the formula P = 1/f, we get P = 1/(-0.02) = -50 D.

 Additional Information

  • Concave Lens
    • A concave lens is also known as a diverging lens.
    • It is thinner at the center and thicker at the edges.
    • It is used in devices such as glasses for nearsightedness and some types of cameras.
Latest RRB JE Updates

Last updated on Jun 7, 2025

-> RRB JE CBT 2 answer key 2025 for June 4 exam has been released at the official website.

-> Check Your Marks via RRB JE CBT 2 Rank Calculator 2025

-> RRB JE CBT 2 admit card 2025 has been released. 

-> RRB JE CBT 2 city intimation slip 2025 for June 4 exam has been released at the official website.

-> RRB JE CBT 2 Cancelled Shift Exam 2025 will be conducted on June 4, 2025 in offline mode. 

-> RRB JE CBT 2 Exam Analysis 2025 is Out, Candidates analysis their exam according to Shift 1 and 2 Questions and Answers.

-> The RRB JE Notification 2024 was released for 7951 vacancies for various posts of Junior Engineer, Depot Material Superintendent, Chemical & Metallurgical Assistant, Chemical Supervisor (Research) and Metallurgical Supervisor (Research). 

-> The selection process includes CBT 1, CBT 2, and Document Verification & Medical Test.

-> The candidates who will be selected will get an approximate salary range between Rs. 13,500 to Rs. 38,425.

-> Attempt RRB JE Free Current Affairs Mock Test here

-> Enhance your preparation with the RRB JE Previous Year Papers

Get Free Access Now
Hot Links: teen patti master gold download teen patti master old version teen patti gold old version