Answer:
The minimum time interval required is 18.1 sec
Step-by-step explanation:
Given:
Magnetic field
T
Minimum induced emf
V
Angle between magnetic field and area vector
34°
Area of door

According to the faraday's law,

Where
magnetic flux
From the formula of magnetic flux,

Initially,


Wb
When door is closed,


Wb
Hence


Wb
Put the values in above equation,


sec
Therefore, the minimum time interval required is 18.1 sec