The quantum number which describes the subshells present in any main shell is called ……………. .

Explanation

**Step-by-Step Solution:**

1. **Understanding Quantum Numbers**: Quantum numbers are values that describe the properties of atomic orbitals and the electrons in those orbitals. There are four main types of quantum numbers: principal quantum number (n), azimuthal quantum number (l), magnetic quantum number (m), and spin quantum number (s).

2. **Identifying the Subshells**: In atomic structure, subshells are subdivisions of electron shells (or energy levels). The subshells are designated as s, p, d, and f, and they correspond to different shapes of the orbitals.

3. **Role of the Azimuthal Quantum Number**: The azimuthal quantum number, denoted by the symbol 'l', is specifically responsible for describing the shape of the subshells within a principal energy level (main shell).

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