Question

Which of the following statements is/are CORRECT about a compound microscope?

1. The focal length of the eyepiece is larger than the focal length of the objective.

2.  The image produced in a normal optical microscope is real.

3. The focal length of the objective lens is equal to the focal length of an eyepiece.

4. The image produced in a normal optical microscope is virtual.

1. Only 1
2. Both 2 and 3
3. 1, 2 and 3
4. Both 1 and 4

Answer 1

Correct Answer - Option 4 : Both 1 and 4

CONCEPT:

Microscope:

• The instrument having a double convex lens with a short focal length that produces an enlarged image of a small object is called a microscope.
• The microscope has two convex lenses- one of them is called an objective lens and another one is known as the eyepiece.​

• The magnification (M) of a microscope is given by:

\(\Rightarrow M\; = \;\frac{L}{{{f_0}}}\left( {\frac{D}{{{f_e}}}} \right)\)

Where L = length of the microscope, D = least distance of clear vision, f0 = focal length of the objective, and fe is the focal length of the eyepiece

EXPLANATION:

• The focal length of the eyepiece lens is larger than the focal length of the objective lens. So statement 1 is correct.
• When an object is placed between the focus and the lens then the image formed by the convex lens is virtual and enlarged.
• As the lens used in the microscope is a convex lens. We observe the object which is very small and near to the lens which makes a virtual and magnified image of the object because the object is placed between focus and lens. Hence statement 4 is correct.