Consider the following statements regarding cathode rays: 1. They originate from the cathode. 2. They are made of electromagnetic waves. 3. They cast shadows. Which are correct? MCQ with Answer and Explanation
Consider the following statements regarding cathode rays: 1. They originate from the cathode. 2. They are made of electromagnetic waves. 3. They cast shadows. Which are correct?
A. 1 and 3 only
B. 2 and 3 only
C. 1 and 2 only
D. 1, 2 and 3
Answer: Option A
Solution (By JKExamLibrary)
Cathode rays are streams of fast-moving electrons, not electromagnetic waves, originating from the cathode in a discharge tube. Because they are material particles traveling in straight lines, they can be stopped by opaque objects, thus casting sharp shadows. Therefore, statements 1 and 3 are correct.
Explanation:
Soap (sodium carboxylate) reacts with Ca²⁺/Mg²⁺ to form insoluble calcium or magnesium carboxylate (scum). This precipitates and reduces cleaning efficiency. Sodium and potassium salts are soluble. This is why detergents, which form soluble Ca/Mg salts, are used. Scum is visible in hard water areas.
Explanation:
pH < 7 indicates acidic. Since 4.5 is less than 7 but not extremely low (like 1-2), it is weakly acidic. Neutral pH=7, basic pH>7. A solution with pH 4 is more acidic than pH 5.
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