With reference to Visible Light Communication (VLC) technology, which of the following statements are correct? 1. VLC uses electromagnetic spectrum wavelengths 375 to 780 nm. 2. VLC is known as long-range optical wireless communication. 3. VLC can transmit large amounts of data faster than Bluetooth. 4. VLC has no electromagnetic interference. Select the correct answer using the code given below:

Answer: C. Statements 1, 3 and 4 are correct; Statement 2 is wrong. VISIBLE LIGHT COMMUNICATION (VLC), often associated with the LiFi (Light Fidelity) technology coined by Harald Haas, is an optical wireless communication technology that uses VISIBLE LIGHT EMITTED FROM LED LAMPS to transmit data. Statement 1 is CORRECT. VLC operates in the visible light portion of the electromagnetic spectrum, with wavelengths broadly in the range of 380 to 780 nm (approximately the 375 to 780 nm range stated). This visible light is modulated at extremely high frequencies, imperceptible to the human eye, while still serving as ordinary illumination. Statement 2 is WRONG. VLC is a SHORT-RANGE optical wireless technology, NOT long-range. Visible light cannot penetrate walls (which is also a security advantage but a coverage limitation), and the practical range is typically a few metres within a room. For long-range optical wireless, FREE SPACE OPTICAL COMMUNICATION (FSOC) using infrared lasers is the relevant technology, not VLC. Statement 3 is CORRECT. VLC offers VERY HIGH DATA RATES. Laboratory demonstrations have achieved multi-gigabit-per-second speeds, far exceeding typical Bluetooth (around 1 to 3 Mbps for classic Bluetooth, up to a few hundred Mbps for advanced LE variants). The high carrier frequency of visible light (around 400 to 800 THz) supports very large bandwidth. Statement 4 is CORRECT. VLC HAS NO RADIO-FREQUENCY ELECTROMAGNETIC INTERFERENCE because visible light does not interact with RF systems. This makes VLC ATTRACTIVE FOR ENVIRONMENTS WHERE RF IS RESTRICTED OR HAZARDOUS: hospitals (sensitive medical equipment), aircraft cabins, nuclear plants, underwater communication, and military secure communications. So 1, 3, 4 are correct; 2 is wrong (VLC is short-range, not long-range). Source: IEEE 802.15.7 Visible Light Communication standard; Haas et al. 'LiFi' publications; UNESCO and IEEE technical references.