Quick Answer: The Concave Lens is a double concave spherical lens of -10D power, 50 mm diameter and 100 mm focal length, used to demonstrate diverging rays and virtual image formation.
Last updated: October 2026
Key Features
Double concave spherical lens
Power -10D with 100 mm focal length
50 mm diameter
Optically worked faces with ground edges
Refractive index approximately 1.52
Technical Specifications
Specification
Value
Lens type
Double concave spherical lens
Power
-10D
Focal length
100 mm
Diameter
50 mm
Refractive index
1.52 approx.
Finish
Optically worked faces with ground edges
About This Product
Parallel or narrow rays are directed through the lens and students see them spread out. Tracing the emergent rays on paper and extending them backwards locates the virtual focus, and the result is compared with the standard concave lens ray diagram. The lens supports lessons on negative focal length, lens power and virtual images, and supports comparison with convex lenses.
Frequently Asked Questions
Q1. Why is the power of this lens negative? A concave lens is a diverging lens, so its focal length and power are taken as negative. This lens has a power of -10D.
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