Which of the following is incorrect?

Options

A. A thin convex lens of focal length `f_(1)` is placed in contact with a thin concave lens of focal length `f_(2)`. The combination will act as convex lens if `f_(1)ltf_(2)`
B. Light on reflection at water-glass boundary will undergo a phase change of `pi`
C. Spherical aberration is minimized by achromatic lens
D. If the image of distant object is formed in front of the retina then defect of vision may be myopia

Answer

To determine which of the given options is incorrect, we will analyze each option step by step.

### Step 1: Analyze Option 1
- **Statement**: A convex lens with focal length \( f_1 \) and a concave lens with focal length \( f_2 \) have their powers defined as \( P_1 = \frac{1}{f_1} \) and \( P_2 = \frac{1}{f_2} \).
- **Analysis**: The power of a convex lens is positive, and the power of a concave lens is negative. If \( f_1 < f_2 \), it implies that \( P_1 > P_2 \) (since \( P_1 \) is positive and \( P_2 \) is negative). This statement is correct.

### Step 2: Analyze Option 2
- **Statement**: When combining lenses, the resultant power is the algebraic sum of the individual powers.
- **Analysis**: This is true. The total power \( P \) of the combination of lenses is given by \( P = P_1 + P_2 \). Therefore, this statement is correct.

### Step 3: Analyze Option 3
- **Statement**: Spherical aberration is minimized by an achromatic lens.
- **Analysis**: This statement is incorrect. Spherical aberration is primarily minimized by using a lens with a suitable aperture or by using aspheric lenses, not specifically by achromatic lenses. Achromatic lenses are designed to minimize chromatic aberration, not spherical aberration.

### Step 4: Analyze Option 4
- **Statement**: If the image of a distinct object is formed in front of the retina, the defect of vision may be myopia.
- **Analysis**: This statement is correct. Myopia (or nearsightedness) occurs when the image of distant objects is formed in front of the retina. Concave lenses are used to correct this vision defect.

### Conclusion
After analyzing all the options, we find that the incorrect statement is **Option 3**.

### Final Answer
The incorrect statement is **Option 3**.

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