To increase angular magnification of magnifying glass, we should increase its

Options

A. aperture
B. focal length
C. power
D. thickness

Explanation

To solve the question about increasing the angular magnification of a magnifying glass, we will follow these steps:

### Step 1: Understand Angular Magnification
Angular magnification (M) is defined as the ratio of the angle subtended by the image (β) at the eye to the angle subtended by the object (α) at the eye when viewed without the magnifying glass. Mathematically, it can be expressed as:
\[ M = \frac{\beta}{\alpha} \]

### Step 2: Identify the Desired Image Position
For a magnifying glass, we want to form the image at the least distance of distinct vision (d), which is typically 25 cm for a normal human eye. This allows the observer to see the image clearly and distinctly.

### Step 3: Use Ray Diagrams
When an object is placed within the focal length of a convex lens (the type used in a magnifying glass), two rays are drawn:
1. A ray parallel to the principal axis that passes through the focus after refraction.
2. A ray that passes through the optical center of the lens without deviation.

These rays will help us find the position of the image formed by the lens.

### Step 4: Relate Angular Magnification to Focal Length
The angular magnification can also be related to the focal length (f) of the lens. The formula derived from the lens formula and the geometry of the situation gives:
\[ M = 1 + \frac{d}{f} \]
Where:
- \( d \) is the least distance of distinct vision (25 cm).
- \( f \) is the focal length of the lens.

### Step 5: Analyze the Effect of Focal Length on Angular Magnification
From the formula, we can see that to increase the angular magnification (M), we need to decrease the focal length (f). This is because as the focal length decreases, the term \( \frac{d}{f} \) increases, thus increasing M.

### Step 6: Consider the Power of the Lens
The power (P) of a lens is defined as the inverse of the focal length:
\[ P = \frac{1}{f} \]
To increase the angular magnification, we need to increase the power of the lens. This means we need to decrease the focal length.

### Conclusion
To increase the angular magnification of a magnifying glass, we should increase its power (which is equivalent to decreasing the focal length).

### Final Answer
**To increase angular magnification of a magnifying glass, we should increase its power.**

---