The space between the outermost filled energy band and the next empty band is called ……….

The space between the outermost filled energy band and the next empty band in a solid is called the band gap or energy gap. This term is primarily used in solid-state physics and semiconductors.

The band gap is crucial because it determines many electronic and optical properties of materials. In semiconductors, a small band gap allows the material to conduct electricity under certain conditions, making it useful for electronic devices. Conversely, insulators have a larger band gap, which makes it difficult for electrons to jump from the valence band to the conduction band, thereby inhibiting electrical conductivity.

Understanding the band gap is essential for the design of materials used in electronic components, including transistors, diodes, and photovoltaic cells. The size of the band gap influences the wavelength of light absorbed or emitted by the material, which is vital in fields like optoelectronics and photovoltaics.