Refrigerator

A method for controlling a refrigerator comprising:

• detecting, at a sensor device, vibrations or sound waves on a front surface of a panel assembly of a door, wherein a portion of the sensor device is provided at a rear side of the front surface of the panel assembly;
• determining whether the detected vibrations or sound waves corresponds to two knock inputs in a predetermined interval;
• in response to the sensor device detecting the two knock inputs in the predetermined interval, turning on an lighting device such that an inner space behind the panel assembly is viewable when the door is closed.

A method for controlling a refrigerator that comprises a cabinet with an inner space, and a door to cover the inner space and including a panel assembly, the panel assembly including a vacuum insulation space, the method comprising:

• receiving a knock input on a front surface of the panel assembly of the door;
• detecting, at a sensor device, the knock input, wherein a portion of the sensor is provided at a rear side of the front surface of the panel assembly;
• in response to the sensor device detecting the knock input, turning on a lighting device such that an inner space behind the panel assembly is viewable through the vacuum insulation space of the panel assembly when the door is closed.