When two plane mirrors are at right angle with each other, the number of image viewed is ______.

Answer

To find the number of images formed when two plane mirrors are placed at right angles (90 degrees) to each other, we can use the formula for calculating the number of images formed by two mirrors:

1. **Understanding the Formula**: The formula for the number of images (N) formed by two plane mirrors inclined at an angle (θ) is given by:
\[ N = \frac{360}{\theta} - 1 \]
Here, θ is the angle between the two mirrors.

2. **Substituting the Angle**: In this case, the angle θ is 90 degrees. We will substitute this value into the formula:
\[ N = \frac{360}{90} - 1 \]

3. **Calculating the Value**: Now, we perform the calculation:
\[ N = 4 - 1 = 3 \]

4. **Conclusion**: Therefore, when two plane mirrors are at right angles to each other, the number of images viewed is **3**.