Focal Length experiment readings

[bishshoy007]

Hello, I need help with the lens experiment, the aim of which is to determine the focal length of a concave lens by combining it coaxially with a convex lens.

Given the focal length of the CONVEX lens is 15cm.
and the focal length of the CONCAVE lens is 30cm.

Can you give me a set of reading, plotting which on the graph paper the slope of the st. line shall give the CONCAVE lens' focal length.

Thanks in advance.

 

[ZapperZ]

Don't you know how to calculate the focal length of a compound lens?

Zz.