In the figure shown, blocks `P` and `Q` are in contact but do not stick to each other. The lower

In the figure shown, blocks `P` and `Q` are in contact but do not stick to each other. The lower face of `P` behaves as a plane mirror. The springs are in their natural lengths. The system is released from rest. Then the distance between `P` and `Q` when `Q` is at the lowest point first time will be