Chemistry 2009 JAMB Past Questions - Question 9: Cathode rays cause an object placed behind a perforated anode to cast a shadow on the screen. This observation shows that the rays

Correct Answer

D

Explanation

The observation that cathode rays cause an object placed behind a perforated anode to cast a shadow on the screen points to the conclusion that the rays:

**Travel in straight lines.**

Here's why:

* **Shadows**: Shadows are formed when an object blocks light or another form of radiation from reaching a surface. In this case, the object casts a shadow because the cathode rays emanating from the cathode cannot reach the screen where they would normally cause a glow.
* **Perforations**: The fact that the anode is perforated and the object still casts a shadow implies that the rays are not simply spreading out randomly in all directions. If they did, some rays would still reach the screen even through the small holes in the anode, preventing a sharp shadow from forming.
* **Straight lines**: Since the object blocks the rays and creates a defined shadow, it suggests that the rays travel in straight lines from the cathode until they hit the object or another obstacle.

Therefore, the observation of the shadow strongly supports the conclusion that cathode rays travel in straight lines. This was a crucial discovery in the early days of understanding electricity and matter, eventually leading to the development of electron microscopes and X-ray technology.