For the same value of n, the penetration power of orbital follows the order

The correct option is f < d < p < s.

Penetration power refers to the ability of an orbital to attract an electron close to the nucleus. An electron in an orbital that is closer to the nucleus experiences a stronger attractive force and is said to have greater penetration power.

For the same principal quantum number (represented by n), the shape and radial distribution of the subshells determine how close their electrons can get to the nucleus. This is dictated by the azimuthal quantum number, l.

The s-orbital (where l = 0) is spherical and has the maximum probability density near the nucleus. It is the most penetrating orbital for a given shell.
The p-orbital (where l = 1) is dumbbell-shaped and is less penetrating than the s-orbital.
The d-orbital (where l = 2) is even more diffused, resulting in lower penetration power.
The f-orbital (where l = 3) is highly diffused and has the least penetration power, meaning its electrons are shielded the most and stay furthest from the nucleus on average.

Therefore, for a constant value of n, the order of penetration power from least to greatest is:

$$f<d<p<s$$