The specific charge for positive rays is much less than the specific charge for cathode rays.
This is because:

Options

A. Positive rays are positively charged
B. Charge on positive rays is less
C. Positive rays comprise ionised atoms whose mass is much higher
D. Experimental method for determination is wrong.

Answer

To solve the question regarding why the specific charge for positive rays is much less than the specific charge for cathode rays, we can break down the explanation into a series of logical steps:

### Step-by-Step Solution:

1. **Understanding Specific Charge**:
- The specific charge is defined as the ratio of charge to mass (specific charge = charge/mass).
- It is a measure of how much charge is present per unit mass of a particle.

2. **Charge and Mass of Positive Rays**:
- Positive rays are primarily composed of protons.
- The charge of a proton is approximately \( +1.6 \times 10^{-19} \) coulombs.
- The mass of a proton is approximately \( 1.67 \times 10^{-27} \) kg.
- Therefore, the specific charge of a proton can be calculated as:
\[ \text{Specific Charge of Positive Rays} = \frac{1.6 \times 10^{-19} \text{ C}}{1.67 \times 10^{-27} \text{ kg}} \approx 9.58 \times 10^{7} \text{ C/kg} \]

3. **Charge and Mass of Cathode Rays**:
- Cathode rays are composed of electrons.
- The charge of an electron is approximately \( -1.6 \times 10^{-19} \) coulombs (we consider the magnitude, so we take \( 1.6 \times 10^{-19} \) C).
- The mass of an electron is approximately \( 9.1 \times 10^{-31} \) kg.
- Therefore, the specific charge of an electron can be calculated as:
\[ \text{Specific Charge of Cathode Rays} = \frac{1.6 \times 10^{-19} \text{ C}}{9.1 \times 10^{-31} \text{ kg}} \approx 1.76 \times 10^{11} \text{ C/kg} \]

4. **Comparison of Specific Charges**:
- From the calculations:
- Specific charge of positive rays (protons) ≈ \( 9.58 \times 10^{7} \text{ C/kg} \)
- Specific charge of cathode rays (electrons) ≈ \( 1.76 \times 10^{11} \text{ C/kg} \)
- It is evident that the specific charge of cathode rays is significantly higher than that of positive rays.

5. **Conclusion**:
- The reason for the difference in specific charge is due to the mass of the particles. Protons (in positive rays) have a much greater mass than electrons (in cathode rays).
- Since the charge of both particles is the same in magnitude, the higher mass of protons leads to a lower specific charge compared to electrons.

### Final Answer:
The specific charge for positive rays is much less than the specific charge for cathode rays because positive rays comprise ionized atoms (like protons) whose mass is much higher than that of electrons in cathode rays.