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When a plane mirror AB is placed horizontally on level ground at a distance of 60 metres from the foot of a tower, the top of the tower and its image in the mirror subtends, an angle of 90° at B. The height of the tower is:
                                         
  • a)
    30 metre
  • b)
    60 metre
  • c)
    90 metre
  • d)
    120 metre.
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
When a plane mirror AB is placed horizontally on level ground at a dis...
The angle subtended at the eye by the top of the tower with respect to the ground is 45 degrees. This happens when the height of the tower is equal to the distance from the eye. The eye is assumed to be very near to the mirror. (Refer below figure).
Angle subtended by AB = 90 degrees/2 = 45 degrees.
Therefore, tanθ=h/60​. That is, tan45=h/60​.So, h=60m.
Hence, the height of the tower is 60 m.
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Most Upvoted Answer
When a plane mirror AB is placed horizontally on level ground at a dis...
The mirror is placed 60 m form the foot of the tower.

Light rays from the top of the tower falling on the mirror suffer a deviation of 90 deg.

Since the mirror is a plane the angle of incidence = angle of reflection = 90/2 = 45 deg. The complement of 45 deg is 45 deg with the ground.

So the height of the tower is 60 cot 45 = 60 m.

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When a plane mirror AB is placed horizontally on level ground at a distance of 60 metres from the foot of a tower, the top of the tower and its image in the mirror subtends, an angle of 90° at B. The height of the tower is: a)30 metreb)60 metrec)90 metred)120 metre.Correct answer is option 'B'. Can you explain this answer? for Class 12 2025 is part of Class 12 preparation. The Question and answers have been prepared according to the Class 12 exam syllabus. Information about When a plane mirror AB is placed horizontally on level ground at a distance of 60 metres from the foot of a tower, the top of the tower and its image in the mirror subtends, an angle of 90° at B. The height of the tower is: a)30 metreb)60 metrec)90 metred)120 metre.Correct answer is option 'B'. Can you explain this answer? covers all topics & solutions for Class 12 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for When a plane mirror AB is placed horizontally on level ground at a distance of 60 metres from the foot of a tower, the top of the tower and its image in the mirror subtends, an angle of 90° at B. The height of the tower is: a)30 metreb)60 metrec)90 metred)120 metre.Correct answer is option 'B'. Can you explain this answer?.
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