1 arsenic
2. antimony
3. indium
4. phosphorous
1. both the objective and the eyepiece has short focal lengths
2. both the objective and the eyepiece have long focal lengths
3. the objective has a short focal length and the eyepiece has a long focal length
4. the objective has a long focal length and the eyepiece has a short focal length
1. The substance completely disintegrates in 20 days
2. The substance completely disintegrates in 40 days
3. 1/8 part of the mass of the substance will be left intact at the end of 40 days
4. 7/8 part of the mass of the substance disintegrates in 30 days