If a point object in denser medium is observed from rarer medium then dap=apparent depthdac=actual depth
Ex:7.1 question number 7
Answer given: p is mid point
Angle BAD=angleABE
Angle EPA=Angle DPB
To prove triangle DAP in congruent to triangle EBP
Proof angle EPA+Angle EPD=angle DPB + angle EPD
Angle APD=angle BPE (1)
In triangle DAP and Triangle EBP
Angle BAD = angle ABE(given)
AP=PB (p is mid point of AB)
Angle APD=Angle BPE (frome 1)
So by asa criteria
Triangle DAP is congruent to triangle EBP