Write the SI unit of luminous intensity and the amount of substance.

Options

A. kg
B. mole
C. candela
D. ampere

Answer

To answer the question regarding the SI units of luminous intensity and the amount of substance, we can break it down into two parts.

### Step 1: Identify the SI unit of luminous intensity
1. **Definition**: Luminous intensity is defined as the amount of luminous flux emitted per unit solid angle.
2. **Formula**: It can be represented mathematically as:
\[ I = \frac{d\Phi}{d\Omega} \]
where \( I \) is the luminous intensity, \( d\Phi \) is the luminous flux, and \( d\Omega \) is the solid angle.
3. **SI Unit**: The SI unit of luminous intensity is the **candela (cd)**. It can also be expressed as:
\[ 1 \text{ candela} = 1 \text{ lumen per steradian} \]

### Step 2: Identify the SI unit of the amount of substance
1. **Definition**: The amount of substance is a measure of the number of entities (such as atoms, molecules, ions, etc.) present in a sample.
2. **SI Unit**: The SI unit for the amount of substance is the **mole (mol)**. One mole is defined as the amount of substance that contains as many entities as there are atoms in 12 grams of carbon-12.

### Final Answer
- The SI unit of luminous intensity is **candela (cd)**.
- The SI unit of the amount of substance is **mole (mol)**.