What is the value of Planck's constant

Options

A. `6.626 xx 10^(-27)Js`
B. `6.626 xx 10^(-34)Js`
C. `6.023 xx 10^(23)Js`
D. `1.602 xx 10^(-19)Js`

Answer

To find the value of Planck's constant, we can follow these steps:

### Step 1: Understand Planck's Constant
Planck's constant (denoted as \( h \)) is a fundamental constant in quantum mechanics. It relates the energy of a photon to its frequency.

### Step 2: Recall the Formula
The energy of a photon can be expressed using the formula:
\[ E = h \nu \]
where:
- \( E \) is the energy in joules,
- \( h \) is Planck's constant,
- \( \nu \) (nu) is the frequency in hertz (Hz), which is equivalent to \( \text{s}^{-1} \).

### Step 3: Determine the Units of Planck's Constant
To find the units of Planck's constant, we can rearrange the formula:
\[ h = \frac{E}{\nu} \]
The units of energy \( E \) are joules (J), and the units of frequency \( \nu \) are \( \text{s}^{-1} \). Therefore, the units of \( h \) are:
\[ \text{Units of } h = \frac{\text{joules}}{\text{s}^{-1}} = \text{joule} \cdot \text{s} \]

### Step 4: Identify the Value of Planck's Constant
The accepted value of Planck's constant is:
\[ h = 6.626 \times 10^{-34} \text{ joule second} \]

### Step 5: Compare with Given Options
Now, we need to compare this value with the options provided:
1. \( 6.626 \times 10^{-27} \text{ J s} \) - Incorrect
2. \( 6.626 \times 10^{-34} \text{ J s} \) - Correct
3. \( 6.023 \times 10^{23} \text{ J s} \) - Incorrect (This is Avogadro's number)
4. \( 1.602 \times 10^{-19} \text{ J s} \) - Incorrect (This is the charge of an electron)

### Conclusion
The correct value of Planck's constant is:
\[ \boxed{6.626 \times 10^{-34} \text{ J s}} \]

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