a compound microscope consists of an objective lens with focal length 1 cm and eye piece of focal length 2 cm and a tube length 20cm the magnification will be approximately

To find the magnification of a compound microscope, we use the formula for total magnification:

Total magnification (M) = Magnification by the objective (M₀) × Magnification by the eyepiece (Mₑ)

Step 1: Magnification by the Objective (M₀)
The magnification by the objective is given by:

M₀ = L / f₀

where:
L = tube length = 20 cm
f₀ = focal length of the objective = 1 cm

Substituting the values:

M₀ = 20 / 1
M₀ = 20

Step 2: Magnification by the Eyepiece (Mₑ)
The magnification by the eyepiece is given by:

Mₑ = 25 / fₑ

where:
The least distance of distinct vision is taken as 25 cm
fₑ = focal length of the eyepiece = 2 cm

Substituting the values:

Mₑ = 25 / 2
Mₑ = 12.5

Step 3: Total Magnification
M = M₀ × Mₑ
M = 20 × 12.5
M = 250

Thus, the approximate magnification of the compound microscope is 250.