the secondary rays from different radiators is not very different, with the exception of substances such as granite, brick, and cement, which give out secondary rays of nearly twice the penetrating power of other substances.
β and γ rays.
| Radiator | Density | Secondary Radiation | Sec. Rad. / Density | Aluminium ·085 cm. λ |
|---|---|---|---|---|
| Mercury | 13·6 | 147 | 10·8 | |
| Lead | 11·4 | 141 | 12·4 | 18·5 |
| Copper | 8·8 | 79 | 9·0 | 20 |
| Brass | 8·4 | 81 | 9·6 | 21 |
| Iron (wrought) | 7·8 | 75 | 9·6 | 20 |
| Tin | 7·4 | 73 | 9·9 | 20·3 |
| Zinc | 7·0 | 79 | 11·3 | |
| Granite | 2·7 | 54 | 20·0 | 12·4 |
| Slate | 2·6 | 53 | 20·4 | 12·1 |
| Aluminium | 2·6 | 42 | 16·1 | 24 |
| Glass | 2·5 | 44 | 17·6 | 24 |
| Cement | 2·4 | 47 | 19·6 | 13·5 |
| Brick | 2·2 | 49 | 22·3 | 13·0 |
| Ebonite | 1·1 | 32 | 29·1 | 26 |
| Water | 1·0 | 24 | 24·0 | 21 |
| Ice | ·92 | 26 | 28·2 | |
| Paraffin solid | ·9 | 17 | 18·8 | 21 |
| „ liquid | ·85 | 16 | 18·8 | |
| Mahogany | ·56 | 21·4 | 38·2 | 23 |
| Paper | ·4? | 21·0 | 52 | 22 |
| Millboard | ·4? | 19·4 | 48 | 20·5 |
| Papier-mâché | ... | 21·9 | ||
| Basswood | ·36 | 20·7 | 57 | 22 |
| Pine | ·35 | 21·8 | 62 | 21 |
| X ray screen | 75·2 | 23·6 |
The secondary radiation not only comes from the surface of the radiator but from a considerable depth. The amount of secondary rays increases with the thickness of the radiator, and, in the case of glass and aluminium,