On an energy level diagram of hydrogen, show by a downward or an upward arrow, a transition which results in :
(i) emission line of Balmer series.
(ii) emission line of Lyman series.
(iii) absorption line of Lyman series.
(b) (i) Define unified atomic mass unit .
(ii) Write the expression for speed of electromagnetic waves in a medium of electrical permittivity `epsilon` and magnetic permeability `mu`.

Explanation

### Step-by-Step Solution

#### Part (a): Energy Level Diagram of Hydrogen

1. **Draw the Energy Levels**:
- Start by drawing the energy levels of hydrogen. Label them as \( n = 1, 2, 3, 4, \ldots \) on the vertical axis, where \( n = 1 \) is the ground state and higher \( n \) values represent excited states.

2. **Emission Line of Balmer Series**:
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