Detailed answer

To prevent sunburn, it is recommended to use a sunscreen with a broad-spectrum protection, which means it protects against both UVA and UVB rays. The SPF, or sun protection factor, indicates the level of protection provided against UVB rays. A sunscreen with SPF 30 or higher is generally recommended as it blocks around 97% of UVB rays. However, it's important to note that SPF only measures the protection against UVB rays and not UVA rays. To ensure adequate protection from both types of rays, look for sunscreens labeled 'broad-spectrum'. It is also important to apply sunscreen generously and reapply every two hours, or more frequently if sweating or swimming. Remember to complement sunscreen with other sun protection measures like seeking shade, wearing protective clothing, and using sunglasses.