What are matter waves ?

Explanation

**Step-by-Step Solution:**

1. **Definition of Matter Waves:**
Matter waves, also known as de Broglie waves, are a fundamental concept in quantum mechanics that describe the wave-like behavior of particles. According to Louis de Broglie, every moving particle or object has an associated wave.

2. **Wave-Particle Duality:**
Matter waves illustrate the principle of wave-particle duality, which states that all matter exhibits both wave-like and particle-like properties. This means that particles such as electrons can behave like waves under certain conditions.

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