What happens to the number of images as the angle between?

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The formula for calculating the number of images formed when two mirrors are placed at an angle $\alpha$ is $360/\alpha$. My question is how many images will be formed when it is a fraction? My teacher told to apply greatest integer function but in some places it says nearest even integer. So can someone please tell what is the correct formula?

Question 8 Exercise 7B

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Answer:

(a) The number of images formed when an object is placed between the two plane mirrors at an angle of 90°, is 3. Three images are formed.

We know that two mirrors kept perpendicular to each other, produce three images for an object that is placed in between them.

i.e, the angle between two mirrors is 60°, n=360°/90° = 4, number of images = n-1 = 4-1 = 3.

(b) The number of images formed if an object is placed between two plane mirrors with an angle of 60°, is five. Five images are formed:

i.e, the angle between two mirrors is 60°, n=360°/60° = 6, number of images = n-1 = 6-1 = 5.

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Answer & Explanation:

1.The number of images produced is inversely proportional to the angle between the two mirrors. The smaller the angle, the larger the picture is shaped . ... If the angle between the two adjacent mirrors becomes smaller, the number of images increases, and vice versa.

2.The number of images produced is inversely proportional to the angle between the two mirrors. The smaller the angle, the larger the picture is shaped.

The number (N) of the image produced at a certain angle between two mirrors can be calculated using the formula: N = 360 / angle between the mirror.   If the angle between the two adjacent mirrors becomes, smaller, the number of images increases, and vice versa.  

The formula for the production of the number of images is:  

       (n = number of pictures)  

        n = (360 angle)-1

3.In determining the number of images formed used the formula N=(360÷ANGLES BETWEEN THE MIRROR)-1

EX. N=(360÷90)-1

=4-1

N=3 - number of images formed in a 90-degree angle

4.the mirrors should be placed in front of each other that is parallel to each other so as to form infinite images.