Apparent depth (normal viewing) (d_app = d/n)

jee-mainjee-advancedneet-ug

d_app = d/n

What each symbol means

SymbolWhat it stands for
dReal depth / thickness of medium (m)
nRefractive index of medium (object side) relative to observer side (usually air n≈1)
d_{\mathrm{app}}Apparent depth seen from nearly normal viewing (m)

When to use this

Standard JEE / NCERT assumptions unless stated (paraxial, thin lens, coherent YDSE sources, etc.).