1. What is Planck's Constant Times Speed of Light?

Planck's constant (h) times the speed of light (c) is a fundamental physical constant that appears in many areas of quantum mechanics and spectroscopy. The product h c is approximately 1.986 × 10^-25 J·m.

2. How Does the Calculator Work?

The calculator uses the simple multiplication:

Where:

• \( h \) — Planck's constant (6.626 × 10^-34 J·s)
• \( c \) — Speed of light (3 × 10⁸ m/s)

Explanation: The product h c converts between energy and wavelength in quantum mechanical calculations.

3. Importance of h c Calculation

Details: The h c product is essential for converting between photon energy and wavelength (E = h c/λ), and appears in equations for atomic spectra, blackbody radiation, and quantum mechanics.

4. Using the Calculator

Tips: Enter Planck's constant in J·s and speed of light in m/s. Default values are provided for convenience.

5. Frequently Asked Questions (FAQ)

Q1: What is the exact value of h c?
A: The 2018 CODATA recommended value is 1.986445857×10^-25 J·m (exact value depends on the latest measurements of h and c).

Q2: Why is h c important in spectroscopy?
A: It provides the conversion factor between photon energy (E) and wavelength (λ) through the relation E = h c/λ.

Q3: Is c exactly 3×10⁸ m/s?
A: No, the exact value is 299,792,458 m/s (by definition since 1983). The calculator uses this exact value when you use the default.

Q4: Does h c change in different materials?
A: While c changes in different media (c = c₀/n), the product h c remains constant as it uses the vacuum speed of light.

Q5: What are common uses of h c?
A: Used in Planck's law, Einstein's photoelectric equation, Rydberg formula, and many quantum mechanical calculations.