Question
Answer the following questions:
When viewing through a compound microscope, our eyes should be positioned not on the eyepiece but a short distance away from it for best viewing. Why? How much should be that short distance between the eye and eyepiece?
Solution
When viewing through a compound microscope, our eyes should be positioned at a short distance away from the eyepiece. The image of the objective lens in the eyepiece is known as the ‘eye-ring’. All the rays (from object), refracted by the objective go through the eye-ring. Therefore, it is an ideal position of our eyes for viewing.
If we position our eyes too close to the eyepiece, the path of light rays would be obstructed and this reduce our field of view. If we position our eyes on the eye-ring and if, the area of the pupil of our eye is greater or equal to the area of the eye-ring, our eyes will collect all the light refracted by the objective lens.
The precise location of the eye-ring naturally depends on the separation between the objective and the eyepiece and the focal length of the eyepiece. When, we view through a microscope by placing our eyes on one end, the ideal distance between the eye and the eyepiece is usually built in the design of the instrument.
If we position our eyes too close to the eyepiece, the path of light rays would be obstructed and this reduce our field of view. If we position our eyes on the eye-ring and if, the area of the pupil of our eye is greater or equal to the area of the eye-ring, our eyes will collect all the light refracted by the objective lens.
The precise location of the eye-ring naturally depends on the separation between the objective and the eyepiece and the focal length of the eyepiece. When, we view through a microscope by placing our eyes on one end, the ideal distance between the eye and the eyepiece is usually built in the design of the instrument.
