A: Ray optics assumes that light travels in a straight line which is disapproved by diffraction effects, yet the ray optics assumption is so commonly used in understanding location and several other properties of images in optical instruments.
R: Typical sizes of apertures involved in ordinary optical instruments are much larger than the wavelength of light.

Options

A. IF both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark(2)
C. IF Assertion is true statement but Reason is false then mark(3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the given question, we need to analyze both the assertion (A) and the reason (R) provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that ray optics assumes light travels in straight lines, which is a fundamental principle of ray optics. This is indeed correct.
- It also mentions that this assumption is disproved by diffraction effects. This is also true; diffraction occurs when light encounters an obstacle or a slit that is comparable in size to its wavelength, causing the light to bend and spread out rather than travel in straight lines.

2. **Understanding the Reason (R)**:
- The reason states that typical sizes of apertures in ordinary optical instruments are much larger than the wavelength of light. This is a crucial point.
- Since the size of the apertures (like lenses and slits) in optical instruments (such as microscopes and telescopes) is much larger than the wavelength of light (which is on the order of nanometers), diffraction effects are negligible in these cases.
- Therefore, in practical applications, the assumption that light travels in straight lines holds true because diffraction does not significantly affect the behavior of light in these instruments.

3. **Conclusion**:
- Both the assertion (A) and the reason (R) are correct.
- The reason provided (R) correctly explains why the assumption made in the assertion (A) is still valid in the context of optical instruments.

4. **Final Answer**:
- Since both the assertion and the reason are correct, and the reason explains the assertion, the correct answer is that both A and R are true, and R is the correct explanation of A.