# Magnification in eye

NOTE: This is a dynamic question. There is just ONE question that is being asked among the following. So please answer that one only according to given conditions:

(Do mention which question is being answered.)

Q.1 (conditions to answer Q.1.1 or Q.1.2)
What does the human eye perceives (in context to magnification):
A) Lateral magnification
B) Angular magnification

Q.1.1
IF only (A) is correct, then why it becomes difficult to distinguish between a small object placed closer and larger object farther.

Q.1.2
IF only (B) is correct, then why do we see object(placed at appropriate distance) through the lens magnified ? Because the formula of magnification is

$$m=\frac {H_{image}}{H_{object}}=\frac {image-distance}{object-distance}$$

Then we can write,

$$\frac {H_{image}}{image-distance}= \frac {H_{object}}{object-distance}$$

This shows that the angular size of object and image is same. so how we see magnification in lens?

## 1 Answer

B is correct. When an object is closer to you, it occupies a larger angular extent: so when you focus on it, it leaves a bigger image on your retina - it looks bigger.

UPDATE when you add a second lens L in between the eye E and the object O, this lens creates a "virtual image" V, which subtends a larger angle as seen at the eye (see the two green lines): • then, as shown in question, the object and image, both subtend equal angles in case of lens. so why we see a magnified image? – alto santa Dec 13 '16 at 16:30
• Perhaps I don't understand your question. When you say "how we see magnification in lens" are you asking about an eye aided by an external lens? – Floris Dec 13 '16 at 16:34
• oh yes, let me include some more details. the magnification seen in lens is actually the magnification seen by the eye aided by lens. and the distance of object and eye is kept fixed: when there is no lens and when there is lens. Now the 'angle subtended' is the angle subtended by object and image at the optical centre of lens. [now the basis of asking this question arises that when i am studying the simple microscope, the case when image is at infinity-we consider angular magnification and for case when image is at not at infinty, we consider linear magnification. Why 2 different cases?] – alto santa Dec 13 '16 at 16:47
• Feel free to ask me to clarify my question to help you answer me @Floris – alto santa Dec 13 '16 at 16:58
• @altosanta - I have drawn a diagram that I hopes clarifies the situation. – Floris Dec 13 '16 at 17:20