a beam of light passes through a perfectly true (non-colloidal) solution
a fine beam of sunlight enters a smoke-filled room through a small hole
light travels through a complete vacuum
sound waves travel through air
Answer
a fine beam of sunlight enters a smoke-filled room through a small hole
Detailed Explanation
The chapter gives the example of a fine beam of sunlight entering a smoke-filled room through a small hole as an instance of the Tyndall effect. — Examisthan.com