Option 1: The statement is correct. Cathode rays are a stream of electrons that originate from the cathode (negatively charged electrode) and travel towards the anode (positively charged electrode) in a cathode-ray discharge tube.

Option 2: The statement is correct. Cathode-ray tubes (CRTs) are used in television picture tubes. CRTs work by using a cathode to emit electrons and a screen coated with phosphors that light up to create the image.

Option 3: The statement is correct. Cathode rays themselves are not visible because they are made up of electrons, which are particles that do not emit visible light. However, their presence can be observed indirectly through their effects, such as when they cause a fluorescent material to emit light.

Option 4: The statement is incorrect. The characteristics of cathode rays do not depend on the nature of the gas present in the cathode-ray tube. Instead, the characteristics depend on the voltage applied across the electrodes and the properties of the electrodes themselves. The nature of the gas can affect the behavior of the cathode-ray discharge, but not the characteristics of the cathode rays themselves.

Alert - The correct statement for option 4 should be: The characteristics of cathode rays do